Multi-layer core golf ball

ABSTRACT

The present invention is directed to an improved multi-layer golf ball displaying enhanced playing characteristics, including high speed, high launch, and low spin. In general the golf ball displays improved performance in areas such as distance and feel for lower swing speed players. The ball has a relatively large solid inner core, with at least one solid outer core layer surrounding the inner core, and a thin cover layer surrounding the outermost core layer. The inner core is softer than the outer core, which in turn is softer than the cover. The ball may be designed such that the coefficient of restitution (COR) gradient is from slow to fast; that is, the inner core has a lower COR than the total core, which has a lower COR than the entire golf ball.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of commonly-owned,co-pending U.S. patent application Ser. No. 11/061,338, filed on Feb.18, 2005 and published as U.S. Patent Pub. No. 2005/0176523, and U.S.patent application Ser. No. 10/773,906, filed on Feb. 6, 2004 now U.S.Pat. No. 7,255,656 and published as U.S. Patent Pub No. 2005/0130767.

FIELD OF THE INVENTION

The invention generally relates to golf balls, and more particularly theinvention is directed to golf balls having multi-layered cores having arelatively soft, low compression inner core surrounded by a relativelyrigid outer core and cover. The golf balls may also compriseintermediate core layers.

BACKGROUND OF THE INVENTION

Two-layer golf balls are typically made with a single solid core encasedby a cover. These balls are generally most popular among recreationalgolfers, because they are durable and provide maximum distance.Typically, the solid core is made of polybutadiene cross-linked withzinc diacrylate and/or similar crosslinking agents. The cover materialis a tough, cut-proof blend of one or more materials known as ionomers,such as SURLYN®, sold commercially by DuPont, FORMION®, soldcommercially by A. Schulman, Inc., or PRIMACOR® or DOWLEX®, both soldcommercially by Dow Chemical Co.

Other multi-layer golf balls may have multiple core layers, multipleintermediate layers, and/or multiple cover layers. They tend to overcomesome of the undesirable features of conventional two-layer balls, suchas hard feel and less control, while maintaining the positiveattributes, such as increased initial velocity and distance. However, itis desirable that multi-layer balls have a “feel” similar to woundballs, especially for more advanced players.

Additionally, the spin rates of golf balls affect the overall control ofthe balls depending on the skill level of the players. Golf balls withlower spin rates exhibit improved distance, but are harder to control onshort shots, such as approaches to greens. Conversely, higher spin ratesafford skilled players more control, but inhibit driving distances. Tostrike a balance between the spin rates and the playing characteristicsof golf balls, additional layers, such as intermediate layers, outercore layers and inner cover layers, are often added to the solid coregolf balls to improve the playing characteristics of the ball.

The patent literature discloses a number of multi-layer golf balls. U.S.Patent Pub. No. 2005-0130767 A1, which is commonly owned andincorporated herein by reference in its entirety, is directed to animproved multi-layer golf ball displaying a certain spin profile. Theball has a generally rigid, thermosetting polybutadiene outer coresurrounding a relatively soft, low compression inner core. The innercore has a hardness that is less than the hardness of the outer core,and a specific gravity that is less than or equal to the specificgravity of the outer core. The inner core and outer core are formulatedto provide a combined overall core compression of greater than about 50.

U.S. Pat. No. 6,685,579, which is commonly owned and incorporated byreference in its entirety, is directed to golf balls having a covercomprising three or more layers: an inner cover layer, an outer coverlayer, and an intermediate cover layer. The outer cover layer comprisesa composition formed of a reactive liquid material, and the combinationof the thickness of the cover layers is about 0.125 inches. Golf ballsprepared accordingly can exhibit substantially the same or highercoefficient of restitution (“COR”), with a decrease in compression orflexural modulus, compared to golf balls of conventional construction.The resultant golf balls typically have a COR of greater than about 0.7and an Atti compression of at least about 40. As used herein, the termcoefficient of restitution for golf balls is defined as the ratio of therebound velocity to the inbound velocity when balls are fired into arigid plate. A discussion of COR and suitable test methods for measuringCOR can be found, for example, in U.S. Pat. No. 6,547,677, which isincorporated herein by reference.

U.S. Patent Pub. No. 2004-0082407 A1, which is also commonly owned andincorporated by reference in its entirety, is directed to a golf ballcomprising an inner core, an outer core, and a cover. At least one layerof the golf ball is made from a low compression, high COR material, andis being supported by a low deformation, high compression layer. Theresulting golf ball has high COR at fast and slow impact speeds and lowcompression for controlled greenside play.

Varying materials, density, or specific gravity among the various layersof a golf ball controls the spin rate of the golf ball. For instance,redistributing weight from the outer layers of the golf ball to theinner layers decreases the moment of inertia of the golf ball, therebyincreasing the spin rate and vice versa as discussed in commonly ownedU.S. Pat. No. 6,494,795 B2.

Hence, there remains a need for multi-layer golf balls with improveddistance and feel for low swing-speed players.

SUMMARY OF THE INVENTION

This invention is directed to a multi-layer golf ball comprising aninner core, a cover layer, and at least one intermediate layer betweenthe inner core and the cover layer. The layers of the ball vary inproperties according to gradients. The coefficient of restitutiongradient from the inner core to the outermost layer is from low to high,or the initial velocity gradient from the inner core to the cover layeris from slow to fast. Similarly, the flexural modulus increases from theinner core to the outer cover layer, as do the compression and thehardness of the layers. These properties produce a golf ball thatprovides improved distance and feel for low swing-speed players.

According to the present invention, the inner core has a compression ofless than about 60, more preferably less than about 40, and mostpreferably less than about 30. The intermediate layer is harder than theinner core, with a hardness greater than about 55 Shore D, and has ahigher specific gravity than that of the inner core. The intermediatelayer also preferably has a higher flexural modulus than the inner core.The cover layer is constructed such that the ratio of the flexuralmodulus in ksi to the Shore D hardness is less than 1.0, more preferablyless than 0.9, and most preferably less than 0.8.

In another aspect of the invention, the specific gravity of the innercore is less than 1.15, and preferably less than 1.05. The specificgravity of the intermediate layer is greater than 1.15, and preferablygreater than 1.20, and most preferably greater than 1.25.

In yet another aspect of the invention, the cover of the ball has ahardness of at least 60 Shore D, more preferably at least 65 Shore D, aflexural modulus of at least 60 ksi, and a thickness of 0.03 to 0.5inches. The cover comprises an acrylic acid ionomer with an acid contentbetween 13% and 16%, and the ionomer is neutralized with a cation.

The present invention is also directed to a golf ball with an innercore, at least one intermediate core layer that has a larger specificgravity than the inner core, at least one outer core layer that has alarger specific gravity than the intermediate core layer, and a coverwith a specific gravity less than the outer core layer. The volume ofthe inner core layer is preferably greater than the volume of the outercore layer, which in turn is greater than the volume of the cover layer.The cover layer is harder than the outer core layer, which is harderthan the inner core layer.

In another aspect of the invention, a multi-layer golf ball withhardness and specific gravity gradients is constructed with at least oneof the core layers comprising a highly neutralized thermoplastic ionomer(HNP). Preferably, the inner core comprises an unfilled HNP having aspecific gravity less than 0.95.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which form a part of the specification andare to be read in conjunction therewith and in which like referencenumerals are used to indicate like parts in the various views:

FIG. 1 is a cross-sectional representation of a golf ball formed inaccordance with a first embodiment of the present invention; and

FIG. 2 is a cross-sectional representation of a golf ball formed inaccordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to multi-layer golf balls having acore, a cover layer, and at least one intermediate layer between thecore and the cover layer. The core, the intermediate layers, and thecover layer may be constructed to have different properties. Severalembodiments of the present invention are described below.

One embodiment of the present invention is a multi-layer golf ballcomprising an inner core, an outer core layer surrounding the innercore, and a cover layer surrounding the core layers. An optionalintermediate core layer may be present inside the outer core layer, butsurrounding the inner core. The inner core preferably has a low specificgravity, a low flexural modulus, and a low hardness. The outer corelayer has a higher specific gravity, a higher flexural modulus, and ahigher hardness than the inner core. The cover has a flexural modulusvalue that is at least the same as that of the outer core layer orhigher. Furthermore, the cover is constructed such that the ratio of thehardness of the cover (in Shore D) divided by the flexural modulus ofthe cover (in ksi) is less than 1.0. In this embodiment, the inner coreis preferably made from polybutadiene, and the cover is preferably madefrom an ionomer, such as an acrylic acid ionomer, have an acid contentof about 13% to 16%. Other suitable materials for the core and coverlayer are discussed below. Preferred properties of the various layers ofthe multi-layer golf ball in this embodiment are specified in the tablebelow:

Inner Core Outer Core Layer Cover Layer Diameter 1.40 0.10 0.04 (Inches)Compression <40 40-80 60-110 (Atti) Specific <1.15 >1.15 <1.0 GravityHardness <40 >55 >60 (Shore D) (But < Flex Modulus) Flexural 1-3020-60 >60 Modulus (ksi) Material Polybutadiene Polybutadiene or AcrylicAcid HNP Ionomer (13%-16% acid)

Another embodiment of the present invention is a multi-layer golf ballthat is substantially similar to the first embodiment. However, in thissecond embodiment there is a COR gradient from slow to fast, e.g., theinner core has a low COR value, the outer core layer has a higher CORvalue, and the cover layer has an even higher COR value.

A third embodiment is also substantially similar to the firstembodiment. However, in this embodiment at least one core layercomprises a highly neutralized thermoplastic ionomer (HNP), andpreferably the inner core of the golf ball comprises an unfilled HNPhaving a specific gravity of about 0.95.

Yet another embodiment of the present invention is directed at amulti-layer golf ball comprising an inner core, at least oneintermediate core layer, an outer core layer, and a cover layer. In thisembodiment, a volume-decreasing gradient is present, e.g., the volume ofthe inner core is larger than volume of the intermediate core layer,which is larger than the volume of the outer core, which is larger thanthe volume of the cover layer. A hardness-increasing gradient is alsopresent, resulting in a hard inner core, a slightly softer intermediatecore layer, a slightly softer outer core layer, and an even softer coverlayer. A specific gravity gradient is also present, progressing from aninner core with a lower specific gravity to an outer core layer with ahigher specific gravity. However, the gradient does not progress all theway through the cover layer, as it is preferred in this embodiment thatthe specific gravity of the outer core layer is higher than the specificgravity of the cover layer.

These characteristics provide for a golf ball that will exhibit highspeed, low spin, and high launch angles, while being able to be designedat relatively low or very low compressions. This combination of featuresis particularly suited to improve distance and feel for casual,recreational golfers who possess lower swing speeds, and the presentinvention is believed to outperform golf balls that are currentlytargeted at that market.

For example, the preferred cover layer of the present invention has ahardness to flexural modulus relationship such that the recreationalgolfer will enjoy low spin (and therefore more distance) off the tee,while still receiving higher spin (and therefore more control) whilehitting approach shots into greens. The lower compression of the ballwill produce a softer feel, which is especially advantageous whenchipping and putting around the greens.

As shown generally in FIGS. 1 and 2, reference numbers 10 and 20designate golf balls in accordance to the present invention. As picturedin FIG. 1, some embodiments of golf ball 10 have an inner core 12, atleast one intermediate core layer 14, an outer core layer 16, and acover layer 18. Other embodiments, such as depicted by golf ball 20 inFIG. 2, may include only inner core 22, outer core layer 24, and coverlayer 26. When the inner core is surrounded by multiple layers aspictured in FIGS. 1 and 2, it is preferable for the multiple layers tohave a gradient in physical/mechanical properties, such as hardness,that increases from outermost to innermost layer or that decreases fromoutermost to innermost layer. Other property gradients in addition tohardness can result from the molding process and use of layers,including velocity, coefficient of restitution, etc.

Any or all of the inner core, intermediate core layers, and outer corelayers of multi-layer golf ball 10 or 20 may comprise thermosetting orthermoplastic materials such as polyurethane, polyurea, partially orfully neutralized ionomers, thermosetting polydiene rubber such aspolybutadiene, polyisoprene, ethylene propylene diene monomer rubber,ethylene propylene rubber, natural rubber, balata, butyl rubber,halobutyl rubber, styrene butadiene rubber or any styrenic blockcopolymer such as styrene ethylene butadiene styrene rubber, etc.,metallocene or other single site catalyzed polyolefin, polyurethanecopolymers, e.g. with silicone, as long as the material meets thegradient criteria described above.

In addition to the materials discussed above, compositions within thescope of the present invention can incorporate one or more polymers.Examples of suitable additional polymers for use in the presentinvention include, but are not limited to, the following: thermoplasticelastomer, thermoset elastomer, synthetic rubber, thermoplasticvulcanizate, copolymeric ionomer, terpolymeric ionomer, polycarbonate,polyolefin, polyamide, copolymeric polyamide, polyesters, polyvinylalcohols, acrylonitrile-butadiene-styrene copolymers, polyarylate,polyacrylate, polyphenylene ether, impact-modified polyphenylene ether,high impact polystyrene, diallyl phthalate polymer, metallocenecatalyzed polymers, styrene-acrylonitrile (SAN) (includingolefin-modified SAN and acrylonitrile-styrene-acrylonitrile),styrene-maleic anhydride (S/MA) polymer, styrenic copolymer,functionalized styrenic copolymer, functionalized styrenic terpolymer,styrenic terpolymer, cellulose polymer, liquid crystal polymer (LCP),ethylene-propylene-diene terpolymer (EPDM), ethylene-vinyl acetatecopolymers (EVA), ethylene-propylene copolymer, ethylene vinyl acetate,polyurea, and polysiloxane or any metallocene-catalyzed polymers ofthese species. Suitable polyamides for use as an additional material incompositions within the scope of the present invention also includeresins obtained by: (1) polycondensation of (a) a dicarboxylic acid,such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine or decamethylenediamine,1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as ε-caprolactam or ω-laurolactam;(3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproicacid, 9-aminononanoic acid, 11-aminoundecanoic acid or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine. Specific examples of suitablepolyamides include Nylon 6, Nylon 66, Nylon 610, Nylon 11, Nylon 12,copolymerized Nylon, Nylon MXD6, and Nylon 46.

Other preferred materials suitable for use as an additional material incore compositions within the scope of the present invention includepolyester elastomers marketed under the tradename SKYPEL by SK Chemicalsof South Korea, or diblock or triblock copolymers marketed under thetradename SEPTON by Kuraray Corporation of Kurashiki, Japan, and KRATONby Kraton Polymers Group of Companies of Chester, United Kingdom. All ofthe materials listed above can provide for particular enhancements toball layers prepared within the scope of the present invention.

Suitable ionomeric polymers (i.e., copolymer or terpolymer-typeionomers) for use as core layers include α-olefin/unsaturated carboxylicacid copolymer-type ionomeric or terpolymer-type ionomeric resins.Copolymeric ionomers are obtained by neutralizing at least a portion ofthe carboxylic groups in a copolymer of an α-olefin and anα,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, with a metalion. Examples of suitable α-olefins include ethylene, propylene,1-butene, and 1-hexene. Examples of suitable unsaturated carboxylicacids include acrylic, methacrylic, ethacrylic, α-chloroacrylic,crotonic, maleic, fumaric, and itaconic acid. Copolymeric ionomersinclude ionomers having varied acid contents and degrees of acidneutralization that are neutralized by monovalent or bivalent cationsdiscussed below.

Terpolymeric ionomers are obtained by neutralizing at least a portion ofcarboxylic groups in a terpolymer of an α-olefin, and an α,β-unsaturatedcarboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturatedcarboxylate having 2 to 22 carbon atoms with metal ion. Examples ofsuitable α-olefins include ethylene, propylene, 1-butene, and 1-hexene.Examples of suitable unsaturated carboxylic acids include acrylic,methacrylic, ethacrylic, α-chloroacrylic, crotonic, maleic, fumaric, anditaconic acid. Terpolymeric ionomers include ionomers having varied acidcontents and degrees of acid neutralization, neutralized by monovalentor bivalent cations as discussed below. Examples of suitable ionomericresins include those marketed under the name SURLYN® manufactured byE.I. du Pont de Nemours & Company of Wilmington, Del., and IOTEK®manufactured by Exxon Mobil Corporation of Irving, Tex.

Silicone materials also are usable as core layers. These can bemonomers, oligomers, prepolymers, or polymers, with or withoutadditional reinforcing filler. One type of silicone material that issuitable can incorporate at least 1 alkenyl group having at least 2carbon atoms in their molecules. Examples of these alkenyl groupsinclude, but are not limited to, vinyl, allyl, butenyl, pentenyl,hexenyl and decenyl. The alkenyl functionality can be located at anylocation of the silicone structure, including one or both terminals ofthe structure. The remaining (i.e., non-alkenyl) silicon-bonded organicgroups in this component are independently selected from hydrocarbon orhalogenated hydrocarbon groups that contain no aliphatic unsaturation.Non-limiting examples of these include: alkyl groups, such as methyl,ethyl, propyl, butyl, pentyl and hexyl; cycloalkyl groups, such ascyclohexyl and cycloheptyl; aryl groups, such as phenyl, tolyl andxylyl; aralkyl groups, such as benzyl and phenethyl, and halogenatedalkyl groups, such as 3,3,3-trifluoropropyl and chloromethyl. Anothertype of silicone material suitable for use in the present invention isone having hydrocarbon groups that lack aliphatic unsaturation. Specificexamples of suitable silicones for use in making compositions of thepresent invention include the following: trimethylsiloxy-endblockeddimethylsiloxane-methylhexenylsiloxane copolymers;dimethylhexenlylsiloxy-endblocked dimethylsiloxane-methylhexenylsiloxanecopolymers; trimethylsiloxy-endblockeddimethylsiloxane-methylvinylsiloxane copolymers;trimethylsiloxy-endblockedmethylphenylsiloxane-dimethylsiloxane-methylvinylsiloxane copolymers;dimethylvinylsiloxy-endblocked dimethylpolysiloxanes;dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxanecopolymers; dimethylvinylsiloxy-endblocked methylphenylpolysiloxanes;dimethylvinylsiloxy-endblockedmethylphenylsiloxane-dimethylsiloxane-methylvinylsiloxane copolymers;and the copolymers listed above, in which at least one end group isdimethylhydroxysiloxy. Commercially available silicones suitable for usein compositions within the scope of the present invention includeSilastic by Dow Corning Corp. of Midland, Mich., Blensil by GE Siliconesof Waterford, N.Y., and Elastosil by Wacker Silicones of Adrian, Mich.

Other types of copolymers also can be added to compositions within thescope of the present invention. Examples of copolymers comprising epoxymonomers and which are suitable for use within the scope of the presentinvention include styrene-butadiene-styrene block copolymers, in whichthe polybutadiene block contains an epoxy group, andstyrene-isoprene-styrene block copolymers, in which the polyisopreneblock contains epoxy. Commercially available examples of these epoxyfunctional copolymers include ESBS A1005, ESBS A1010, ESBS A1020, ESBSAT018, and ESBS AT019, marketed by Daicel Chemical Industries, Ltd. ofOsaka, Japan.

A preferred embodiment for a slow core layer comprises polybutadiene,SBR, little or no zinc diacrylate (from 0-10 parts), optional zincdimethacrylate, or a non zinc salt unsaturated monomer such astrimethylol propane triacrylate (SR-350 sold by the Sartomer Co.), aperoxide initiator. Other formulations for the core are disclosed inco-pending commonly owned U.S. Pub. No. 2005-0255941 A1, which isincorporated herein by reference in its entirety. Alternatively, anon-peroxide, sulfur vulcanized formulation, such as that disclosed inU.S. Pat. No. 7,041,008 can be used. This reference is incorporated byreference herein in its entirety.

The core diameter ranges from about 0.100 inch to about 1.64 inch,preferably from about 1.00 inch to about 1.62 inch. Typical corediameter ranges from 0.25 inch to 1.625 inch in increments of 0.05 inch.Common core sizes are 0.050 inch, 1.00 inch, 1.10 inches, 1.20 inches,1.30 inches, 1.40 inches, 1.45 inches, 1.50 inches, 1.55 inches, 1.57inches, 1.58 inches, 1.59 inches, and 1.60 inches. The sizes of the coreplus any intermediate layer or layers may be within the same size orsize range as the core sizes above, or may be slightly larger.

Other suitable materials for the core include, but are not limited to:

(1) Polyurethanes, such as those prepared from polyols and diisocyanatesor polyisocyanates and those disclosed in U.S. Pat. Nos. 5,334,673 and6,506,851 and 6,663,564;

(2) Polyureas, such as those disclosed in U.S. Pat. Nos. 5,484,870 and6,835,794; and

(3) Polyurethane-urea hybrids, blends or copolymers comprising urethaneor urea segments.

The core of the multi-layer golf ball preferably includes a polyurethanecomposition comprising the reaction product of at least onepolyisocyanate and at least one curing agent. The curing agent caninclude, for example, one or more diamines, one or more polyols, or acombination thereof. The polyisocyanate can be combined with one or morepolyols to form a prepolymer, which is then combined with the at leastone curing agent. Thus, the polyols described herein are suitable foruse in one or both components of the polyurethane material, i.e., aspart of a prepolymer and in the curing agent.

The core or any layer in the golf ball can also be made fromhighly-neutralized polymers and blends thereof (“HNP”). The acidmoieties of the HNP's, typically ethylene-based ionomers, are preferablyneutralized greater than about 70%, more preferably greater than about90%, and most preferably at least about 100%. The HNP's can be also beblended with a second polymer component, which, if containing an acidgroup, may be neutralized in a conventional manner, by the organic fattyacids of the present invention, or both. The second polymer component,which may be partially or fully neutralized, preferably comprisesionomeric copolymers and terpolymers, ionomer precursors,thermoplastics, polyamides, polycarbonates, polyesters, polyurethanes,polyureas, thermoplastic elastomers, polybutadiene rubber, balata,metallocene-catalyzed polymers (grafted and non-grafted), single-sitepolymers, high-crystalline acid polymers, cationic ionomers, and thelike. HNP polymers typically have a material hardness of between about20 and about 80 Shore D, and a flexural modulus of between about 3 ksiand about 200 ksi.

In one embodiment of the present invention the HNP's are ionomers and/ortheir acid precursors that are preferably neutralized, either fully orpartially, with organic acid copolymers or the salts thereof. The acidcopolymers are preferably α-olefin, such as ethylene, C₃₋₈α,β-ethylenically unsaturated carboxylic acid, such as acrylic andmethacrylic acid, copolymers. They may optionally contain a softeningmonomer, such as alkyl acrylate and alkyl methacrylate, wherein thealkyl groups have from 1 to 8 carbon atoms.

The acid copolymers can be described as E/X/Y copolymers where E isethylene, X is an α,β-ethylenically unsaturated carboxylic acid, and Yis a softening comonomer. In a preferred embodiment, X is acrylic ormethacrylic acid and Y is a C₁₋₈ alkyl acrylate or methacrylate ester. Xis preferably present in an amount from about 1 to about 35 weightpercent of the polymer, more preferably from about 5 to about 30 weightpercent of the polymer, and most preferably from about 10 to about 20weight percent of the polymer. Y is preferably present in an amount fromabout 0 to about 50 weight percent of the polymer, more preferably fromabout 5 to about 25 weight percent of the polymer, and most preferablyfrom about 10 to about 20 weight percent of the polymer.

Specific acid-containing ethylene copolymers include, but are notlimited to, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate,ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylicacid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate,ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/methacrylic acid/methyl methacrylate, andethylene/acrylic acid/n-butyl methacrylate. Preferred acid-containingethylene copolymers include, ethylene/methacrylic acid/n-butyl acrylate,ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/acrylic acid/ethyl acrylate, ethylene/methacrylicacid/ethyl acrylate, and ethylene/acrylic acid/methyl acrylatecopolymers. The most preferred acid-containing ethylene copolymers are,ethylene/(meth)acrylic acid/n-butyl, acrylate, ethylene/(meth)acrylicacid/ethyl acrylate, and ethylene/(meth)acrylic acid/methyl acrylatecopolymers.

Ionomers are typically neutralized with a metal cation, such as lithium,sodium, potassium, magnesium, calcium, barium, lead, tin, zinc,aluminum, or a mixture thereof. It has been found that by addingsufficient organic acid or salt of organic acid, along with a suitablebase, to the acid copolymer or ionomer, however, the ionomer can beneutralized, without losing processability, to a level much greater thanfor a metal cation. Preferably, the acid moieties are neutralizedgreater than about 80%, preferably from 90-100%, most preferably 100%without losing processability. This accomplished by melt-blending anethylene α,β-ethylenically unsaturated carboxylic acid copolymer, forexample, with an organic acid or a salt of organic acid, and adding asufficient amount of a cation source to increase the level ofneutralization of all the acid moieties (including those in the acidcopolymer and in the organic acid) to greater than 90%, (preferablygreater than 100%).

The organic acids of the present invention are aliphatic, mono- ormulti-functional (saturated, unsaturated, or multi-unsaturated) organicacids. Salts of these organic acids may also be employed. The salts oforganic acids of the present invention include the salts of barium,lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium,strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver,aluminum, tin, or calcium, salts of fatty acids, particularly stearic,bebenic, erucic, oleic, linoelic or dimerized derivatives thereof. It ispreferred that the organic acids and salts of the present invention berelatively non-migratory (they do not bloom to the surface of thepolymer under ambient temperatures) and non-volatile (they do notvolatilize at temperatures required for melt-blending).

The ionomers of the invention may also be partially neutralized withmetal cations alone. The acid moiety in the acid copolymer isneutralized about 1 to about 100%, preferably at least about 40 to about100%, and more preferably at least about 90 to about 100%, to form anionomer by a cation such as lithium, sodium, potassium, magnesium,calcium, barium, lead, tin, zinc, aluminum, or a mixture thereof.

The acid copolymers of the present invention are prepared from ‘direct’acid copolymers, copolymers polymerized by adding all monomerssimultaneously, or by grafting of at least one acid-containing monomeronto an existing polymer.

Thermoplastic polymer components, such as copolyetheresters,copolyesteresters, copolyetheramides, elastomeric polyolefins, styrenediene block copolymers and their hydrogenated derivatives,copolyesteramides, thermoplastic polyurethanes, such ascopolyetheturethanes, copolyesterurethanes, copolyureaurethanes,epoxy-based polyurethanes, polycaprolactone-based polyurethanes,polyureas, and polycarbonate-based polyurethanes fillers, and otheringredients, if included, can be blended in either before, during, orafter the acid moieties are neutralized, thermoplastic polyurethanes.

The copolyetheresters are comprised of a multiplicity of recurring longchain units and short chain units joined head-to-tail through esterlinkages, the long chain units being represented by the formula:

and the short chain units being represented by the formula:

where G is a divalent radical remaining after the removal of terminalhydroxyl groups from a poly(alkylene oxide)glycol having a molecularweight of about 400-8000 and a carbon to oxygen ratio of about 2.0-4.3;R is a divalent radical remaining after removal of hydroxyl groups froma diol having a molecular weight less than about 250; provided saidshort chain ester units amount to about 15-95 percent by weight of saidcopolyetherester. The preferred copolyetherester polymers are thosewhere the polyether segment is obtained by polymerization oftetrahydrofuran and the polyester segment is obtained by polymerizationof tetramethylene glycol and phthalic acid. For purposes of theinvention, the molar ether:ester ratio can vary from 90:10 to 10:80;preferably 80:20 to 60:40; and the Shore D hardness is less than 70;preferably less than about 40.

The copolyetheramides are comprised of a linear and regular chain ofrigid polyamide segments and flexible polyether segments, as representedby the general formula:

wherein PA is a linear saturated aliphatic polyamide sequence formedfrom a lactam or amino acid having a hydrocarbon chain containing 4 to14 carbon atoms or from an aliphatic C₆-C₈ diamine, in the presence of achain-limiting aliphatic carboxylic diacid having 4-20 carbon atoms;said polyamide having an average molecular weight between 300 and15,000; and PB is a polyoxyalkylene sequence formed from linear orbranched aliphatic polyoxyalkylene glycols, mixtures thereof orcopolyethers derived therefrom, said polyoxyalkylene glycols having amolecular weight of less than or equal to 6000; and n indicates asufficient number of repeating units so that said polyetheramidecopolymer has an intrinsic viscosity of from about 0.6 to about 2.05.The preparation of these polyetheramides comprises the step of reactinga dicarboxylic polyamide, the COOH groups of which are located at thechain ends, with a polyoxyalkylene glycol hydroxylated at the chainends, in the presence of a catalyst such as a tetra-alkyl ortho titanatehaving the general formula Ti(OR)_(x) wherein R is a linear branchedaliphatic hydrocarbon radical having 1 to 24 carbon atoms. Again, themore polyether units incorporated into the copolyetheramide, the softerthe polymer. The ether:amide ratios are as described above for theether:ester ratios, as is the Shore D hardness.

The elastomeric polyolefins are polymers composed of ethylene and higherprimary olefins such as propylene, hexene, octene, and optionally1,4-hexadiene and or ethylidene norbornene or norbornadiene. Theelastomeric polyolefins can be optionally functionalized with maleicanhydride, epoxy, hydroxy, amine, carboxylic acid, sulfonic acid, orthiol groups.

Thermoplastic polyurethanes are linear or slightly chain branchedpolymers consisting of hard blocks and soft elastomeric blocks. They areproduced by reacting soft hydroxy terminated elastomeric polyethers orpolyesters with diisocyanates, such as methylene diisocyanate (“MDI”),p-phenylene diisocyanate (“PPDI”), or toluene diisocyanate (“TDI”).These polymers can be chain extended with glycols, secondary diamines,diacids, or amino alcohols. The reaction products of the isocyanates andthe alcohols are called urethanes, and these blocks are relatively hardand high melting. These hard, high melting blocks are responsible forthe thermoplastic nature of the polyurethanes.

Block styrene diene copolymers and their hydrogenated derivatives arecomposed of polystyrene units and polydiene units. They may also befunctionalized with moieties such as OH, NH₂, epoxy, COOH, and anhydridegroups. The polydiene units are derived from polybutadiene, polyisopreneunits, or copolymers of these two. In the case of the copolymer it ispossible to hydrogenate the polyolefin to give a saturated rubberybackbone segments. These materials are usually referred to as SBS, SIS,or SEBS thermoplastic elastomers and they can also be functionalizedwith maleic anhydride.

Grafted metallocene-catalyzed polymers are also useful for blending withthe HNP's of the present invention. The grafted metallocene-catalyzedpolymers, while conventionally neutralized with metal cations, may alsobe neutralized, either partially for fully, with organic acids or saltsthereof and an appropriate base. Grafted metallocene-catalyzed polymers,such as those disclosed in U.S. Pat. Nos. 5,703,166; 5,824,746;5,981,658; and 6,025,442, which are incorporated herein by reference,useful in the golf balls of the invention are available in experimentalquantities from DuPont under the tradenames SURLYN® NMO 525D, SURLYN®NMO 524D, and SURLYN® NMO 499D, all formerly known as the FUSABOND®family of polymers, or may be obtained by subjecting a non-graftedmetallocene-catalyzed polymer to a post-polymerization reaction toprovide a grafted metallocene-catalyzed polymer with the desired pendantgroup or groups. Examples of metallocene-catalyzed polymers to whichfunctional groups may be grafted for use in the invention include, butare not limited to, homopolymers of ethylene and copolymers of ethyleneand a second olefin, preferably, propylene, butene, pentene, hexene,heptene, octene, and norbornene. Generally, the invention includes golfballs having at least one layer comprising at least one graftedmetallocene-catalyzed polymer or polymer blend, where the graftedmetallocene-catalyzed polymer is produced by grafting a functional grouponto a metallocene-catalyzed polymer having the formula:

wherein R₁ is hydrogen, branched or straight chain alkyl such as methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, carbocyclic, oraromatic; R₂ is hydrogen, lower alkyl including C₁-C₅; carbocyclic, oraromatic; R₃ is hydrogen, lower alkyl including C₁-C₅, carbocyclic, oraromatic; R₄ is selected from the group consisting of H, C_(n)H_(2n+1),where n=1 to 18, and phenyl, in which from 0 to 5H within R₄ can bereplaced by substituents COOH, SO₃H, NH₂, F, Cl, Br, I, OH, SH,silicone, lower alkyl esters and lower alkyl ethers, with the provisothat R₃ and R₄ can be combined to form a bicyclic ring; R₅ is hydrogen,lower alkyl including C₁-C₅, carbocyclic, or aromatic; R₆ is hydrogen,lower alkyl including C₁-C₅, carbocyclic, or aromatic; and wherein x, yand z are the relative percentages of each co-monomer. X can range fromabout 1 to 99 percent or more preferably from about 10 to about 70percent and most preferred, from about 10 to 50 percent. Y can be from99 to 1 percent, preferably, from 90 to 30 percent, or most preferably,90 to 50 percent. Z can range from about 0 to about 49 percent. One ofordinary skill in the art would understand that if an acid moiety ispresent as a ligand in the above polymer that it may be neutralized upto 100% with an organic fatty acid as described above.

Metallocene-catalyzed copolymers or terpolymers can be random or blockand may be isotactic, syndiotactic, or atactic. The pendant groupscreating the isotactic, syndiotactic, or atactic polymers are chosen todetermine the interactions between the different polymer chains makingup the resin to control the final properties of the resins used in golfball covers, cores, or intermediate layers. As will be apparent to thoseskilled in the art, grafted metallocene-catalyzed polymers useful in theinvention that are formed from metallocene-catalyzed random or blockcopolymers or terpolymers will also be random or block copolymers orterpolymers, and will have the same tacticity of themetallocene-catalyzed polymer backbone.

As used herein, the term “phrase branched or straight chain alkyl” meansany substituted or unsubstituted acyclic carbon-containing compounds.Examples of alkyl groups include lower alkyl, for example, methyl,ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or t-butyl; upper alkyl,for example, octyl, nonyl, decyl, and the like; and lower alkylene, forexample, ethylene, propylene, butylene, pentene, hexene, octene,norbornene, nonene, decene, and the like.

In addition, such alkyl groups may also contain various substituents inwhich one or more hydrogen atoms has been replaced by a functionalgroup. Functional groups include, but are not limited to hydroxyl,amino, carboxyl, sulfonic amide, ester, ether, phosphates, thiol, nitro,silane and halogen (fluorine, chlorine, bromine and iodine), to mentionbut a few.

As used herein, the term “substituted and unsubstituted carbocyclic”means cyclic carbon-containing compounds, including, but not limited tocyclopentyl, cyclohexyl, cycloheptyl, and the like. Such cyclic groupsmay also contain various substituents in which one or more hydrogenatoms has been replaced by a functional group. Such functional groupsinclude those described above, and lower alkyl groups having from 1-28carbon atoms. The cyclic groups of the invention may further comprise aheteroatom.

As mentioned above, R₁ and R₂ can also represent any combination ofalkyl, carbocyclic or aryl groups, for example, 1-cyclohexylpropyl,benzyl cyclohexylmethyl, 2-cyclohexylpropyl, 2,2-methylcyclohexylpropyl,2,2-methylphenylpropyl, and 2,2-methylphenylbutyl.

Non-grafted metallocene-catalyzed polymers useful in the presentinvention are commercially available under the trade name AFFINITY®polyolefin plastomers and ENGAGE® polyolefin elastomers, commerciallyavailable from Dow Chemical Company and DuPont-Dow. Other commerciallyavailable metallocene-catalyzed polymers can be used, such as EXACT®,commercially available from Exxon, and INSIGHT®, commercially availablefrom Dow. The EXACT® and INSIGHT® line of polymers also have novelrheological behavior in addition to their other properties as a resultof using a metallocene catalyst technology. Metallocene-catalyzedpolymers are also readily available from Sentinel Products Corporationof Hyannis, Mass., as foamed sheets for compression molding.

Monomers useful in the present invention include, but are not limitedto, olefinic monomers having, as a functional group, sulfonic acid,sulfonic acid derivatives, such as chlorosulfonic acid, vinyl ethers,vinyl esters, primary, secondary, and tertiary amines, mono-carboxylicacids, dicarboxylic acids, partially or fully ester-derivatizedmono-carboxylic and dicarboxylic acids, anhydrides of dicarboxylicacids, and cyclic imides of dicarboxylic acids.

In addition, metallocene-catalyzed polymers may also be functionalizedby sulfonation, carboxylation, or the addition of an amine or hydroxygroup. Metallocene-catalyzed polymers functionalized by sulfonation,carboxylation, or the addition of a hydroxy group may be converted toanionic ionomers by treatment with a base. Similarly,metallocene-catalyzed polymers functionalized by the addition of anamine may be converted to cationic ionomers by treatment with an alkylhalide, acid, or acid derivative.

The most preferred monomer is maleic anhydride, which, once attached tothe metallocene-catalyzed polymer by the post-polymerization reaction,may be further subjected to a reaction to form a graftedmetallocene-catalyzed polymer containing other pendant or functionalgroups. For example, reaction with water will convert the anhydride to adicarboxylic acid; reaction with ammonia, alkyl, or aromatic amine formsan amide; reaction with an alcohol results in the formation of an ester;and reaction with a base results in the formation of an anionic ionomer.

The HNP's of the present invention may also be blended with single-siteand metallocene catalysts and polymers formed therefrom. As used herein,the term “single-site catalyst,” such as those disclosed in U.S. Pat.No. 6,150,462 which is incorporated herein by reference, refers to acatalyst that contains an ancillary ligand that influences the stearicand electronic characteristics of the polymerizing site in a manner thatprevents formation of secondary polymerizing species. The term“metallocene catalyst” refers to a single-site catalyst wherein theancillary ligands comprise substituted or unsubstituted cyclopentadienylgroups, and the term “non-metallocene catalyst” refers to a single-sitecatalyst other than a metallocene catalyst.

Non-metallocene single-site catalysts include, but are not limited to,the Brookhart catalyst, which has the following structure:

wherein M is nickel or palladium; R and R′ are independently hydrogen,hydrocarbyl, or substituted hydrocarbyl; Ar is (CF₃)₂C₆H₃, and X isalkyl, methyl, hydride, or halide; the McConville catalyst, which hasthe structure:

wherein M is titanium or zirconium; Iron (II) and cobalt (II) complexeswith 2,6-bis(imino)pyridyl ligands, which have the structure:

where M is the metal, and R is hydrogen, alkyl, or hydrocarbyl; Titaniumor zirconium complexes with pyrroles as ligands also serve assingle-site catalysts. These complexes have the structure:

where M is the metal atom; m and n are independently 1 to 4, andindicate the number of substituent groups attached to the aromaticrings; R_(m) and R_(n) are independently hydrogen or alkyl; and X ishalide or alkyl. Other examples include diimide complexes of nickel andpalladium, which have the structure:

where Ar is aromatic, M is the metal, and X is halide or alkyl.Boratabenzene complexes of the Group IV or V metals also function assingle-site catalysts. These complexes have the structure.

and

where B is boron and M is the metal atom.

As used herein, the term “single-site catalyzed polymer” refers to anypolymer, copolymer, or terpolymer, and, in particular, any polyolefinpolymerized using a single-site catalyst. The term “non-metallocenesingle-site catalyzed polymer” refers to any polymer, copolymer, orterpolymer, and, in particular, any polyolefin polymerized using asingle-site catalyst other than a metallocene-catalyst. The catalystsdiscussed above are examples of non-metallocene single-site catalysts.The term “metallocene catalyzed polymer” refers to any polymer,copolymer, or terpolymer, and, in particular, any polyolefin,polymerized using a metallocene catalyst.

As used herein, the term “single-site catalyzed polymer blend” refers toany blend of a single-site catalyzed polymer and any other type ofpolymer, preferably an ionomer, as well as any blend of a single-sitecatalyzed polymer with another single-site catalyzed polymer, including,but not limited to, a metallocene-catalyzed polymer.

The terms “grafted single-site catalyzed polymer” and “graftedsingle-site catalyzed polymer blend” refer to any single-site catalyzedpolymer or single-site catalyzed polymer blend in which the single-sitecatalyzed polymer has been subjected to a post-polymerization reactionto graft at least one functional group onto the single-site catalyzedpolymer. A “post-polymerization reaction” is any reaction that occursafter the formation of the polymer by a polymerization reaction.

The single-site catalyzed polymer, which may be grafted, may also beblended with polymers, such as non-grafted single-site catalyzedpolymers, grafted single-site catalyzed polymers, ionomers, andthermoplastic elastomers. Preferably, the single-site catalyzed polymeris blended with at least one ionomer of the preset invention.

Grafted single-site catalyzed polymers useful in the golf balls of theinvention may be obtained by subjecting a non-grafted single-sitecatalyzed polymer to a post-polymerization reaction to provide a graftedsingle-site catalyzed polymer with the desired pendant group or groups.Examples of single-site catalyzed polymers to which functional groupsmay be grafted for use in the invention include, but are not limited to,homopolymers of ethylene and propylene and copolymers of ethylene and asecond olefin, preferably, propylene, butene, pentene, hexene, heptene,octene, and norbornene. Monomers useful in the present inventioninclude, but are not limited to olefinic monomers having as a functionalgroup sulfonic acid, sulfonic acid derivatives, such as chlorosulfonicacid, vinyl ethers, vinyl esters, primary, secondary, and tertiaryamines, epoxies, isocyanates, mono-carboxylic acids, dicarboxylic acids,partially or fully ester derivatized mono-carboxylic and dicarboxylicacids, anhydrides of dicarboxylic acids, and cyclic imides ofdicarboxylic acids. Generally, this embodiment of the invention includesgolf balls having at least one layer comprising at least one graftedsingle-site catalyzed polymer or polymer blend, where the graftedsingle-site catalyzed polymer is produced by grafting a functional grouponto a single-site catalyzed polymer having the formula:

where R₁ is hydrogen, branched or straight chain alkyl such as methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl, carbocyclic,aromatic or heterocyclic; R₂, R₃, R₅, and R₆ are hydrogen, lower alkylincluding C₁-C₅, carbocyclic, aromatic or heterocyclic; R₄ is H,C_(n)H_(2n+1), where n=1 to 18, and phenyl, in which from 0 to 5 Hwithin R₄ can be replaced by substituents such as COOH, SO₃H, NH₂, F,Cl, Br, I, OH, SH, epoxy, isocyanate, silicone, lower alkyl esters andlower alkyl ethers; also, R₃ and R₄ can be combined to form a bicyclicring; and x, y and z are the relative percentages of each co-monomer. Xcan range from about 1 to about 100 percent or more preferably from 1 to70 percent and most preferred, from about 1 to about 50 percent. Y canbe from about 99 to about 0 percent, preferably, from about 9 to about30 percent, or most preferably, about 9 to about 50 percent. Z can rangefrom about 0 to about 50 percent. One of ordinary skill in the art wouldalso understand that if an acid group is selected as a ligand in theabove structure that it too could be neutralized with the organic fattyacids described above.

The HNP's of the present invention may also be blended with highcrystalline acid copolymers and their ionomer derivatives (which may beneutralized with conventional metal cations or the organic fatty acidsand salts thereof) or a blend of a high crystalline acid copolymer andits ionomer derivatives and at least one additional material, preferablyan acid copolymer and its ionomer derivatives. As used herein, the term“high crystalline acid copolymer” is defined as a “product-by-process”in which an acid copolymer or its ionomer derivatives formed from aethylene/carboxylic acid copolymer comprising about 5 to about 35percent by weight acrylic or methacrylic acid, wherein the copolymer ispolymerized at a temperature of about 130° C. to 200° C., at pressuresgreater than about 20 ksi preferably greater than about 25 ksi, morepref. from about 25 ksi to about 50 ksi, wherein up to about 70 percent,preferably 100 percent, of the acid groups are neutralized with a metalion, organic fatty acids and salts thereof, or a mixture thereof. Thecopolymer can have a melt index (“MI”) of from about 20 to about 300g/10 min, preferably about 20 to about 200 g/10 min, and uponneutralization of the copolymer, the resulting acid copolymer and itsionomer derivatives should have an MI of from about 0.1 to about 30.0g/10 min.

Suitable high crystalline acid copolymer and its ionomer derivativescompositions and methods for making them are disclosed in U.S. Pat. No.5,580,927, the disclosure of which is hereby incorporated by referencein its entirety.

The high crystalline acid copolymer or its ionomer derivatives employedin the present invention are preferably formed from a copolymercontaining about 5 to about 35 percent, more preferably from about 9 toabout 18, most preferably about 10 to about 13 percent, by weight ofacrylic acid, wherein up to about 75 percent, most preferably about 60percent, of the acid groups are neutralized with an organic fatty acid,salt thereof, or a metal ion, such as sodium, lithium, magnesium, orzinc ion.

Generally speaking, high crystalline acid copolymer and its ionomerderivatives are formed by polymerization of their base copolymers atlower temperatures, but at equivalent pressures to those used forforming a conventional acid copolymer and its ionomer derivatives.Conventional acid copolymers are typically polymerized at apolymerization temperature of from at least about 200° C. to about 270°C., preferably about 220° C., and at pressures of from about 23 to about30 ksi. In comparison, the high crystalline acid copolymer and itsionomer derivatives employed in the present invention are produced fromacid copolymers that are polymerized at a polymerization temperature ofless than 200° C., and preferably from about 130° C. to about 200° C.,and at pressures from about 20 to about 50 ksi.

The HNP's of the present invention may also be blended with cationicionomers, such as those disclosed in U.S. Pat. No. 6,193,619 which isincorporated herein by reference. In particular, cationic ionomers havea structure according to the formula:

or the formula:

wherein R₁-R₉ are organic moieties of linear or branched chain alkyl,carbocyclic, or aryl; and Z is the negatively charged conjugate ionproduced following alkylation and/or quaternization. The cationicpolymers may also be quarternized up to 100% by the organic fatty acidsdescribed above.

In addition, such alkyl group may also contain various substituents inwhich one or more hydrogen atoms has been replaced by a functionalgroup. Functional groups include but are not limited to hydroxyl, amino,carboxyl, amide, ester, ether, sulfonic, siloxane, siloxyl, silanes,sulfonyl, and halogen.

As used herein, substituted and unsubstituted carbocyclic groups of upto about 20 carbon atoms means cyclic carbon-containing compounds,including but not limited to cyclopentyl, cyclohexyl, cycloheptyl, andthe like. Such cyclic groups may also contain various substituents inwhich one or more hydrogen atoms has been replaced by a functionalgroup. Such functional groups include those described above, and loweralkyl groups as described above. The cyclic groups of the invention mayfurther comprise a heteroatom.

The HNP's of the present invention may also be blended with polyurethaneand polyurea ionomers which include anionic moieties or groups, such asthose disclosed in U.S. Pat. No. 6,207,784 which is incorporated hereinby reference. Typically, such groups are incorporated onto thediisocyanate or diisocyanate component of the polyurethane or polyureaionomers. The anionic group can also be attached to the polyol or aminecomponent of the polyurethane or polyurea, respectively. Preferably, theanionic group is based on a sulfonic, carboxylic or phosphoric acidgroup. Also, more than one type of anionic group can be incorporatedinto the polyurethane or polyurea. Examples of anionic polyurethaneionomers with anionic groups attached to the diisocyanate moiety canhave a chemical structure according to the following formula:

where A=R-Z⁻M^(+x); R is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; Z=SO₃ ⁻, CO₂ ⁻ or HPO₃ ⁻; M is a groupIA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB or VIIIBmetal; x=1 to 5; B is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; and n=1 to 100. Preferably, M^(+x) is oneof the following: Li⁺, Na⁺, K⁺, Mg⁺², Zn⁺², Ca⁺², Mn⁺², Al⁺³, Ti^(+x),Zr^(+x), W^(+x) or Hf^(+x).

Exemplary anionic polyurethane ionomers with anionic groups attached tothe polyol component of the polyurethane are characterized by the abovechemical structure where A is a straight chain or branched aliphaticgroup, a substituted straight chain or branched aliphatic group, or anaromatic or substituted aromatic group; B=R-Z⁻M^(+x); R is a straightchain or branched aliphatic group, a substituted straight chain orbranched aliphatic group, or an aromatic or substituted aromatic group;Z=SO₃ ⁻, CO₂ ⁻ or HPO₃ ⁻; M is a group IA, IB, IIA, IIB, IIIA, IIIB,IVA, IVB, VA, VB, VIA, VIB, VIIB or VIIIB metal; x=1 to 5; and n=1 to100. Preferably, M^(+x) is one of the following: Li⁺, Na⁺, K⁺, Mg⁺²,Zn⁺², Ca⁺², Mn⁺², Al⁺³, Ti^(+x), Zr^(+x), W^(+x) or Hf^(+x).

Examples of suitable anionic polyurea ionomers with anionic groupsattached to the diisocyanate component have a chemical structureaccording to the following chemical structure:

where A=R-Z⁻M^(+x); R is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; Z=SO₃ ⁻, CO₂ ⁻ or HPO₃ ⁻; M is a groupIA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIA, VIB, VIIB or VIIIBmetal; x=1 to 5; and B is a straight chain or branched aliphatic group,a substituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group. Preferably, M^(+x) is one of thefollowing: Li⁺, Na⁺, K⁺, Mg⁺², Zn⁺², Ca⁺², Mn⁺², Al⁺³, Ti^(+x), Zr^(+x),W^(+x), or Hf^(+x).

Suitable anionic polyurea ionomers with anionic groups attached to theamine component of the polyurea are characterized by the above chemicalstructure where A is a straight chain or branched aliphatic group, asubstituted straight chain or branched aliphatic group, or an aromaticor substituted aromatic group; B=R-Z-M^(+x); R is a straight chain orbranched aliphatic group, a substituted straight chain or branchedaliphatic group, or an aromatic or substituted aromatic group; Z=SO₃ ⁻,CO₂ ⁻, or HPO₃ ⁻; M is a group IA, IB, IIA, IIB, IIIA, IIIB, IVA, IVB,VA, VB, VIA, VIB, VIIB or VIIIB metal; and x=1 to 5. Preferably, M^(+x)is one of the following: Li⁺, Na⁺, K⁺, Mg⁺², Zn⁺², Ca⁺², Mn⁺², Al⁺³,Ti^(+x), Zr^(+x), W^(+x), or Hf^(+x). The anionic polyurethane andpolyurea ionomers may also be neutralized up to 100% by the organicfatty acids described above.

The anionic polymers useful in the present invention, such as thosedisclosed in U.S. Pat. No. 6,221,960 which is incorporated herein byreference, include any homopolymer, copolymer or terpolymer havingneutralizable hydroxyl and/or dealkylable ether groups, and in which atleast a portion of the neutralizable or dealkylable groups areneutralized or dealkylated with a metal ion.

As used herein “neutralizable” or “dealkylable” groups refer to ahydroxyl or ether group pendent from the polymer chain and capable ofbeing neutralized or dealkylated by a metal ion, preferably a metal ionbase. These neutralized polymers have improved properties critical togolf ball performance, such as resiliency, impact strength and toughnessand abrasion resistance. Suitable metal bases are ionic compoundscomprising a metal cation and a basic anion. Examples of such basesinclude hydroxides, carbonates, acetates, oxides, sulfides, and thelike.

The particular base to be used depends upon the nature of the hydroxylor ether compound to be neutralized or dealkylated, and is readilydetermined by one skilled in the art. Preferred anionic bases includehydroxides, carbonates, oxides and acetates.

The metal ion can be any metal ion which forms an ionic compound withthe anionic base. The metal is not particularly limited, and includesalkali metals, preferably lithium, sodium or potassium; alkaline earthmetals, preferably magnesium or calcium; transition metals, preferablytitanium, zirconium, or zinc; and Group III and IV metals. The metal ioncan have a +1 to +5 charge. Most preferably, the metal is lithium,sodium, potassium, zinc, magnesium, titanium, tungsten, or calcium, andthe base is hydroxide, carbonate or acetate.

The anionic polymers useful in the present invention include those whichcontain neutralizable hydroxyl and/or dealkylable ether groups.Exemplary polymers include ethylene vinyl alcohol copolymers, polyvinylalcohol, polyvinyl acetate, poly(p-hydroxymethylene styrene), andp-methoxy styrene, to name but a few. It will be apparent to one skilledin the art that many such polymers exist and thus can be used in thecompositions of the invention. In general, the anionic polymer can bedescribed by the chemical structure:

where R₁ is OH, OC(O)R_(a), O-M^(+V), (CH₂)_(n)R_(b),(CHR_(z))_(n)R_(b), or aryl, wherein n is at least 1, R_(a) is a loweralkyl, M is a metal ion, V is an integer from 1 to 5, R_(b) is OH,OC(O)R_(a), O-M^(+V), and R_(z) is a lower alkyl or aryl, and R₂, R₃ andR₄ are each independently hydrogen, straight-chain or branched-chainlower alkyl. R₂, R₃ and R₄ may also be similarly substituted. Preferablyn is from 1 to 12, more preferably 1 to 4.

The term “substituted,” as used herein, means one or more hydrogen atomshas been replaced by a functional group. Functional groups include, butare not limited to, hydroxyl, amino, carboxyl, sulfonic, amide, ether,ether, phosphates, thiol, nitro, silane, and halogen, as well as manyothers which are quite familiar to those of ordinary skill in this art.

The terms “alkyl” or “lower alkyl,” as used herein, includes a group offrom about 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms.

In the anionic polymers useful in the present invention, at least aportion of the neutralizable or dealkylable groups of R₁ are neutralizedor dealkylated by an organic fatty acid, a salt thereof, a metal base,or a mixture thereof to form the corresponding anionic moiety. Theportion of the neutralizable or dealkylable groups which are neutralizedor dealkylated can be between about 1 to about 100 weight percent,preferably between about 50 to about 100 weight percent, more preferablybefore about 90 to about 100.

Neutralization or dealkylation may be performed by melting the polymerfirst, then adding a metal ion in an extruder. The degree ofneutralization or dealkylation is controlled by varying the amount ofmetal ion added. Any method of neutralization or dealkylation availableto those of ordinary skill in the art may also be suitably employed.

In one embodiment, the anionic polymer is repeating units any one of thethree homopolymer units in the chemical structure above. In a preferredembodiment, R₂, R₃, and R₄ are hydrogen, and R₁ is hydroxyl, i.e., theanionic polymer is a polyvinyl alcohol homopolymer in which a portion ofthe hydroxyl groups have been neutralized with a metal base. In anotherpreferred embodiment, R₂, R₃ and R₄ are hydrogen, R₁ is OC(O)R_(a), andR_(a) is methyl, i.e., the anionic polymer is a polyvinyl acetatehomopolymer in which a portion of the methyl ether groups have beendealkylated with a metal ion.

The anionic polymer can also be a copolymer of two different repeatingunits having different substituents, or a terpolymer of three differentrepeating units described in the above formula. In this embodiment, thepolymer can be a random copolymer, an alternating copolymer, or a blockcopolymer, where the term “copolymer” includes terpolymers.

In another embodiment, the anionic polymer is a copolymer, wherein R₅,R₆, R₇, and R₈ are each independently selected from the group definedabove for R₂. The first unit of the copolymer can comprise from about 1to 99 percent weight percent of the polymer, preferably from about 5 to50 weight percent, and the second unit of the copolymer can comprisefrom about 99 to 1 weight percent, preferably from about 95 to 50 weightpercent. In one preferred embodiment, the anionic polymer is a random,alternating, or block copolymer of units (Ia) and (Ib) wherein R₁ ishydroxyl, and each of the remaining R groups is hydrogen, i.e., thepolymer is a copolymer of ethylene and vinyl alcohol. In anotherpreferred embodiment, the anionic polymer is a random, alternating orblock copolymer of units (Ia) and (Ib) wherein R₁ is OC(O)R₅, where R₅is methyl, and each of the remaining R groups is hydrogen, i.e., thepolymer is a copolymer of ethylene and vinyl acetate.

In another embodiment, the anionic polymer is an anionic polymer havingneutralizable hydroxyl and/or dealkylable ether groups of as in theabove chemical structure wherein R₁₋₉ and R_(b) and R_(z) are as definedabove; R₁₀₋₁₁ are each independently selected from the group as definedabove for R₂; and R₁₂ is OH or OC(O)R₁₃, where R₁₃ is a lower alkyl;wherein x, y and z indicate relative weight percent of the differentunits. X can be from about 99 to about 50 weight percent of the polymer,y can be from about 1 to about 50 weight percent of the polymer, and zranges from about 0 to about 50 weight percent of the polymer. At leasta portion of the neutralizable groups R₁ are neutralized. When theamount of z is greater than zero, a portion of the groups R₁₀ can alsobe fully or partially neutralized, as desired.

In particular, the anionic polymers and blends thereof can comprisecompatible blends of anionic polymers and ionomers, such as the ionomersdescribed above, and ethylene acrylic methacrylic acid ionomers, andtheir terpolymers, sold commercially under the trade names SURLYN® andIOTEK® by DuPont and Exxon, respectively. The anionic polymer blendsuseful in the golf balls of the invention can also include otherpolymers, such as polyvinylalcohol, copolymers of ethylene and vinylalcohol, poly(ethylethylene), poly(heptylethylene),poly(hexyldecylethylene), poly(isopentylethylene), poly(butyl acrylate),acrylate), poly(2-ethylbutyl acrylate), poly(heptyl acrylate),poly(2-methylbutyl acrylate), poly(3-methylbutyl acrylate),poly(N-octadecylacrylamide), poly(octadecyl methacrylate),poly(butoxyethylene), poly(methoxyethylene), poly(pentyloxyethylene),poly(1,1-dichloroethylene), poly(4-[(2-butoxyethoxy)methyl]styrene),poly[oxy(ethoxymethyl)ethylene], poly(oxyethylethylene),poly(oxytetramethylene), poly(oxytrimethylene), poly(silanes) andpoly(silazanes), polyamides, polycarbonates, polyesters, styrene blockcopolymers, polyetheramides, polyurethanes, main-chain heterocyclicpolymers and poly(furan tetracarboxylic acid diimides), as well as theclasses of polymers to which they belong.

The anionic polymer compositions of the present invention typically havea flexural modulus of from about 0.5 ksi to about 300 ksi, preferablyfrom about 2 to about 200 ksi. The anionic polymer compositionstypically have a material hardness of at least about 15 Shore A,preferably between about 30 Shore A and 80 Shore D, more preferablybetween about 50 Shore A and 60 Shore D. The loss tangent, ordissipation factor, is a ratio of the loss modulus over the dynamicshear storage modulus, and is typically less than about 1, preferablyless than about 0.01, and more preferably less than about 0.001 for theanionic polymer compositions measured at about 23° C. The specificgravity is typically greater than about 0.7, preferably greater thanabout 1, for the anionic polymer compositions. The dynamic shear storagemodulus, or storage modulus, of the anionic polymer compositions atabout 23° C. is typically at least about 10,000 dyn/cm².

The base rubber typically includes natural or synthetic rubbers. Apreferred base rubber is 1,4-polybutadiene having a cis-structure of atleast 40%. More preferably, the base rubber compriseshigh-Mooney-viscosity rubber. If desired, the polybutadiene can also bemixed with other elastomers known in the art such as natural rubber,polyisoprene rubber and/or styrene-butadiene rubber in order to modifythe properties of the core.

The crosslinking agent includes a metal salt of an unsaturated fattyacid such as a zinc salt or a magnesium salt of an unsaturated fattyacid having 3 to 8 carbon atoms such as acrylic or methacrylic acid.Suitable cross linking agents include metal salt diacrylates,dimethacrylates and monomethacrylates wherein the metal is magnesium,calcium, zinc, aluminum, sodium, lithium or nickel. The crosslinkingagent is present in an amount from about 15 to about 30 parts perhundred of the rubber, preferably in an amount from about 19 to about 25parts per hundred of the rubber and most preferably having about 20 to24 parts crosslinking agent per hundred of rubber. The core compositionsof the present invention may also include at least one organic orinorganic cis-trans catalyst to convert a portion of the cis-isomer ofpolybutadiene to the trans-isomer, as desired.

The initiator agent can be any known polymerization initiator whichdecomposes during the cure cycle. Suitable initiators include peroxidecompounds such as dicumyl peroxide, 1,1-di-(t-butylperoxy)3,3,5-trimethyl cyclohexane, a-a bis-(t-butylperoxy)diisopropylbenzene,2,5-dimethyl-2,5 di-(t-butylperoxy)hexane or di-t-butyl peroxide andmixtures thereof.

Fillers, which can be any compound or composition used to vary thedensity and other properties of the core, typically include materialssuch as tungsten, zinc oxide, barium sulfate, silica, calcium carbonate,zinc carbonate, metals, metal oxides and salts, regrind (recycled corematerial typically ground to about 30 mesh particle),high-Mooney-viscosity rubber regrind, and the like.

The golf ball cores of the present invention may comprise a variety ofconstructions. Although as mentioned above, the materials used for eachlayer may be similar or nearly identical, the characteristics andproperties of each layer may be modified as appropriate in accordancewith the embodiments of the present invention.

The cover layer may include one or more homopolymeric or copolymericmaterials, such as:

-   -   (1) Vinyl resins, such as those formed by the polymerization of        vinyl chloride, or by the copolymerization of vinyl chloride        with vinyl acetate, acrylic esters or vinylidene chloride;    -   (2) Polyolefins, such as polyethylene, polypropylene,        polybutylene and copolymers such as ethylene methylacrylate,        ethylene ethylacrylate, ethylene vinyl acetate, ethylene        methacrylic or ethylene acrylic acid or propylene acrylic acid        and copolymers and homopolymers produced using a single-site        catalyst or a metallocene catalyst;    -   (3) Polyurethanes, such as those prepared from polyols and        diisocyanates or polyisocyanates, in particular PPDI-based        thermoplastic polyurethanes, and those disclosed in U.S. Pat.        No. 5,334,673;    -   (4) Polyureas, such as those disclosed in U.S. Pat. No.        5,484,870;    -   (5) Polyamides, such as poly(hexamethylene adipamide) and others        prepared from diamines and dibasic acids, as well as those from        amino acids such as poly(caprolactam), and blends of polyamides        with SURLYN®, polyethylene, ethylene copolymers,        ethylene-propylene-non-conjugated diene terpolymer, and the        like;    -   (6) Acrylic resins and blends of these resins with poly vinyl        chloride, elastomers, and the like;    -   (7) Thermoplastics, such as urethane; olefinic thermoplastic        rubbers, such as blends of polyolefins with        ethylene-propylene-non-conjugated diene terpolymer; block        copolymers of styrene and butadiene, isoprene or        ethylene-butylene rubber; or copoly(ether-amide), such as        PEBAX®, sold by ELF Atochem of Philadelphia, Pa.;    -   (8) Polyphenylene oxide resins or blends of polyphenylene oxide        with high impact polystyrene as sold under the trademark NORYL®        by General Electric Company of Pittsfield, Mass.;    -   (9) Thermoplastic polyesters, such as polyethylene        terephthalate, polybutylene terephthalate, polyethylene        terephthalate/glycol modified, poly(trimethylene terepthalate),        and elastomers sold under the trademarks HYTREL® by E.I. DuPont        de Nemours & Co. of Wilmington, Del., and LOMOD® by General        Electric Company of Pittsfield, Mass.;    -   (10) Blends and alloys, including polycarbonate with        acrylonitrile butadiene styrene, polybutylene terephthalate,        polyethylene terephthalate, styrene maleic anhydride,        polyethylene, elastomers, and the like, and polyvinyl chloride        with acrylonitrile butadiene styrene or ethylene vinyl acetate        or other elastomers; and    -   (11) Blends of thermoplastic rubbers with polyethylene,        propylene, polyacetal, nylon, polyesters, cellulose esters, and        the like.

In one embodiment, the outer cover preferably includes a polyurethanecomposition comprising the reaction product of at least onepolyisocyanate, polyol, and at least one curing agent. Anypolyisocyanate available to one of ordinary skill in the art is suitablefor use according to the invention. Exemplary polyisocyanates include,but are not limited to, 4,4′-diphenylmethane diisocyanate (“MDI”);polymeric MDI; carbodiimide-modified liquid MDI;4,4′-dicyclohexylmethane diisocyanate (“H₁₂MDI”); p-phenylenediisocyanate (“PPDI”); m-phenylene diisocyanate (“MPDI”); toluenediisocyanate (“TDI”); 3,3′-dimethyl-4,4′-biphenylene diisocyanate(“TODI”); isophoronediisocyanate (“IPDI”); hexamethylene diisocyanate(“HDI”); naphthalene diisocyanate (“NDI”); xylene diisocyanate (“XDI”);p-tetramethylxylene diisocyanate (“p-TMXDI”); m-tetramethylxylenediisocyanate (“m-TMXDI”); ethylene diisocyanate;propylene-1,2-diisocyanate; tetramethylene-1,4-diisocyanate; cyclohexyldiisocyanate; 1,6-hexamethylene-diisocyanate (“HDI”);dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; methylcyclohexylene diisocyanate; triisocyanate of HDI; triisocyanate of2,4,4-trimethyl-1,6-hexane diisocyanate (“TMDI”); tetracenediisocyanate; napthalene diisocyanate; anthracene diisocyanate;isocyanurate of toluene diisocyanate; uretdione of hexamethylenediisocyanate; and mixtures thereof. Polyisocyanates are known to thoseof ordinary skill in the art as having more than one isocyanate group,e.g., di-isocyanate, tri-isocyanate, and tetra-isocyanate. Preferably,the polyisocyanate includes MDI, PPDI, TDI, or a mixture thereof, andmore preferably, the polyisocyanate includes MDI. It should beunderstood that, as used herein, the term “MDI” includes4,4′-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modifiedliquid MDI, and mixtures thereof and, additionally, that thediisocyanate employed may be “low free monomer,” understood by one ofordinary skill in the art to have lower levels of “free” monomerisocyanate groups, typically less than about 0.1% free monomer groups.Examples of “low free monomer” diisocyanates include, but are notlimited to Low Free Monomer MDI, Low Free Monomer TDI, and Low FreeMonomer PPDI.

The at least one polyisocyanate should have less than about 14%unreacted NCO groups. Preferably, the at least one polyisocyanate has nogreater than about 7.5% NCO, and more preferably, less than about 7.0%.

Any polyol available to one of ordinary skill in the art is suitable foruse according to the invention. Exemplary polyols include, but are notlimited to, polyether polyols, hydroxy-terminated polybutadiene(including partially/fully hydrogenated derivatives), polyester polyols,polycaprolactone polyols, and polycarbonate polyols. In one preferredembodiment, the polyol includes polyether polyol. Examples include, butare not limited to, polytetramethylene ether glycol (“PTMEG”),polyethylene propylene glycol, polyoxypropylene glycol, and mixturesthereof. The hydrocarbon chain can have saturated or unsaturated bondsand substituted or unsubstituted aromatic and cyclic groups. Preferably,the polyol of the present invention includes PTMEG.

In another embodiment, polyester polyols are included in thepolyurethane material of the invention. Suitable polyester polyolsinclude, but are not limited to, polyethylene adipate glycol;polybutylene adipate glycol; polyethylene propylene adipate glycol;o-phthalate-1,6-hexanediol; poly(hexamethylene adipate)glycol; andmixtures thereof. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups.

In another embodiment, polycaprolactone polyols are included in thematerials of the invention. Suitable polycaprolactone polyols include,but are not limited to, 1,6-hexanediol-initiated polycaprolactone,diethylene glycol initiated polycaprolactone, trimethylol propaneinitiated polycaprolactone, neopentyl glycol initiated polycaprolactone,1,4-butanediol-initiated polycaprolactone, and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds, orsubstituted or unsubstituted aromatic and cyclic groups.

In yet another embodiment, the polycarbonate polyols are included in thepolyurethane material of the invention. Suitable polycarbonates include,but are not limited to, polyphthalate carbonate and poly(hexamethylenecarbonate)glycol. The hydrocarbon chain can have saturated orunsaturated bonds, or substituted or unsubstituted aromatic and cyclicgroups. In one embodiment, the molecular weight of the polyol is fromabout 200 to about 4000.

Polyamine curatives are also suitable for use in the polyurethanecomposition of the invention and have been found to improve cut, shear,and impact resistance of the resultant balls. Preferred polyaminecuratives include, but are not limited to,3,5-dimethylthio-2,4-toluenediamine and isomers thereof;3,5-diethyltoluene-2,4-diamine and isomers thereof, such as3,5-diethyltoluene-2,6-diamine;4,4′-bis-(sec-butylamino)-diphenylmethane;1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline);4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”);polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenylmethane; p,p′-methylene dianiline (“MDA”); m-phenylenediamine (“MPDA”);4,4′-methylene-bis-(2-chloroaniline) (“MOCA”);4,4′-methylene-bis-(2,6-diethylaniline) (“MDEA”);4,4′-methylene-bis-(2,3-dichloroaniline) (“MDCA”);4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane; 2,2′,3,3′-tetrachloro diamino diphenylmethane; trimethylene glycoldi-p-aminobenzoate; and mixtures thereof. Preferably, the curing agentof the present invention includes 3,5-dimethylthio-2,4-toluenediamineand isomers thereof, such as ETHACURE 300, commercially available fromAlbermarle Corporation of Baton Rouge, La. Suitable polyamine curatives,which include both primary and secondary amines, preferably havemolecular weights ranging from about 64 to about 2000.

At least one of a diol, triol, tetraol, or hydroxy-terminated curativesmay be added to the aforementioned polyurethane composition. Suitablediol, triol, and tetraol groups include ethylene glycol; diethyleneglycol; polyethylene glycol; propylene glycol; polypropylene glycol;lower molecular weight polytetramethylene ether glycol;1,3-bis(2-hydroxyethoxy) benzene;1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene;1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene; 1,4-butanediol;1,5-pentanediol; 1,6-hexanediol; resorcinol-di-(β-hydroxyethyl)ether;hydroquinone-di-(β-hydroxyethyl)ether; and mixtures thereof. Preferredhydroxy-terminated curatives include 1,3-bis(2-hydroxyethoxy)benzene;1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene;1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene; 1,4-butanediol,and mixtures thereof. Preferably, the hydroxy-terminated curatives havemolecular weights ranging from about 48 to 2000. It should be understoodthat molecular weight, as used herein, is the absolute weight averagemolecular weight and would be understood as such by one of ordinaryskill in the art.

Both the hydroxy-terminated and amine curatives can include one or moresaturated, unsaturated, aromatic, and cyclic groups. Additionally, thehydroxy-terminated and amine curatives can include one or more halogengroups. The polyurethane composition can be formed with a blend ormixture of curing agents. If desired, however, the polyurethanecomposition may be formed with a single curing agent.

In a preferred embodiment of the present invention, saturatedpolyurethanes are used to form the outer cover layer, and may beselected from among both castable thermoset and thermoplasticpolyurethanes.

In this embodiment, the saturated polyurethanes of the present inventionare substantially free of aromatic groups or moieties. Saturatedpolyurethanes suitable for use in the invention are a product of areaction between at least one polyurethane prepolymer and at least onesaturated curing agent. The polyurethane prepolymer is a product formedby a reaction between at least one saturated polyol and at least onesaturated diisocyanate. As is well known in the art, a catalyst may beemployed to promote the reaction between the curing agent and theisocyanate and polyol.

Saturated diisocyanates which can be used include, without limitation,ethylene diisocyanate; propylene-1,2-diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (“HDI”);2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; dicyclohexylmethanediisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,3-diisocyanate; cyclohexane-1,4diisocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; isophoronediisocyanate (“IPDI”); methyl cyclohexylene diisocyanate; triisocyanateof HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane diisocyanate(“TMDI”). The most preferred saturated diisocyanates are4,4′-dicyclohexylmethane diisocyanate (“HMDI”) and isophoronediisocyanate (“IPDI”).

Saturated polyols which are appropriate for use in this inventioninclude without limitation polyether polyols such as polytetramethyleneether glycol and poly(oxypropylene)glycol. Suitable saturated polyesterpolyols include polyethylene adipate glycol, polyethylene propyleneadipate glycol, polybutylene adipate glycol, polycarbonate polyol andethylene oxide-capped polyoxypropylene diols. Saturated polycaprolactonepolyols which are useful in the invention include diethyleneglycol-initiated polycaprolactone, 1,4-butanediol-initiatedpolycaprolactone, 1,6-hexanediol-initiated polycaprolactone; trimethylolpropane-initiated polycaprolactone, neopentyl glycol initiatedpolycaprolactone, and polytetramethylene ether glycol-initiatedpolycaprolactone. The most preferred saturated polyols arepolytetramethylene ether glycol and PTMEG-initiated polycaprolactone.

Suitable saturated curatives include 1,4-butanediol, ethylene glycol,diethylene glycol, polytetramethylene ether glycol, propylene glycol;trimethanolpropane; tetra-(2-hydroxypropyl)-ethylenediamine; isomers andmixtures of isomers of cyclohexyldimethylol, isomers and mixtures ofisomers of cyclohexane bis(methylamine); triisopropanolamine; ethylenediamine; diethylene triamine; triethylene tetramine; tetraethylenepentamine; 4,4′-dicyclohexylmethane diamine;2,2,4-trimethyl-1,6-hexanediamine; 2,4,4-trimethyl-1,6-hexanediamine;diethyleneglycol di-(aminopropyl)ether;4,4′-bis-(sec-butylamino)-dicyclohexylmethane;1,2-bis-(sec-butylamino)cyclohexane;1,4-bis-(sec-butylamino)cyclohexane; isophorone diamine; hexamethylenediamine; propylene diamine; 1-methyl-2,4-cyclohexyl diamine;1-methyl-2,6-cyclohexyl diamine; 1,3-diaminopropane; dimethylaminopropylamine; diethylamino propylamine; imido-bis-propylamine; isomersand mixtures of isomers of diaminocyclohexane; monoethanolamine;diethanolamine; triethanolamine; monoisopropanolamine; anddiisopropanolamine. The most preferred saturated curatives are1,4-butanediol, 1,4-cyclohexyldimethylol and4,4′-bis-(sec-butylamino)-dicyclohexylmethane.

The compositions of the invention may also be polyurea-based, which aredistinctly different from polyurethane compositions, but also result indesirable aerodynamic and aesthetic characteristics when used in golfball components. The polyurea-based compositions are preferablysaturated in nature.

Without being bound to any particular theory, it is now believed thatsubstitution of the long chain polyol segment in the polyurethaneprepolymer with a long chain polyamine oligomer soft segment to form apolyurea prepolymer improves shear, cut, and resiliency, as well asadhesion to other components. Thus, the polyurea compositions of thisinvention may be formed from the reaction product of an isocyanate andpolyamine prepolymer crosslinked with a curing agent. For example,polyurea-based compositions of the invention may be prepared from atleast one isocyanate, at least one polyether amine, and at least onediol curing agent or at least one diamine curing agent.

Any polyamine available to one of ordinary skill in the art is suitablefor use in the polyurea prepolymer. Polyether amines are particularlysuitable for use in the prepolymer. As used herein, “polyether amines”refer to at least polyoxyalkyleneamines containing primary amino groupsattached to the terminus of a polyether backbone. Due to the rapidreaction of isocyanate and amine, and the insolubility of many ureaproducts, however, the selection of diamines and polyether amines islimited to those allowing the successful formation of the polyureaprepolymers. In one embodiment, the polyether backbone is based ontetramethylene, propylene, ethylene, trimethylolpropane, glycerin, andmixtures thereof.

Suitable polyether amines include, but are not limited to,methyldiethanolamine; polyoxyalkylenediamines such as,polytetramethylene ether diamines, polyoxypropylenetriamine, andpolyoxypropylene diamines; poly(ethylene oxide capped oxypropylene)etherdiamines; propylene oxide-based triamines; triethyleneglycoldiamines;trimethylolpropane-based triamines; glycerin-based triamines; andmixtures thereof. In one embodiment, the polyether amine used to formthe prepolymer is JEFFAMINE® D2000 (manufactured by Huntsman ChemicalCo. of Austin, Tex.).

The molecular weight of the polyether amine for use in the polyureaprepolymer may range from about 100 to about 5000. As used herein, theterm “about” is used in connection with one or more numbers or numericalranges, should be understood to refer to all such numbers, including allnumbers in a range. In one embodiment, the polyether amine molecularweight is about 200 or greater, preferably about 230 or greater. Inanother embodiment, the molecular weight of the polyether amine is about4000 or less. In yet another embodiment, the molecular weight of thepolyether amine is about 600 or greater. In still another embodiment,the molecular weight of the polyether amine is about 3000 or less. Inyet another embodiment, the molecular weight of the polyether amine isbetween about 1000 and about 3000, and more preferably is between about1500 to about 2500. Because lower molecular weight polyether amines maybe prone to forming solid polyureas, a higher molecular weight oligomer,such as Jeffamine D2000, is preferred.

In one embodiment, the polyether amine has the generic structure:

wherein the repeating unit x has a value ranging from about 1 to about70. More preferably, the repeating unit may be from about 5 to about 50,and even more preferably is from about 12 to about 35.

In another embodiment, the polyether amine has the generic structure:

wherein the repeating units x and z have combined values from about 3.6to about 8 and the repeating unit y has a value ranging from about 9 toabout 50, and wherein R is —(CH₂)_(a)—, where “a” may be a repeatingunit ranging from about 1 to about 10.

In yet another embodiment, the polyether amine has the genericstructure:H₂N—(R)—O—(R)—O—(R)—NH₂wherein R is —(CH₂)_(a)—, and “a” may be a repeating unit ranging fromabout 1 to about 10.

As briefly discussed above, some amines may be unsuitable for reactionwith the isocyanate because of the rapid reaction between the twocomponents. In particular, shorter chain amines are fast reacting. Inone embodiment, however, a hindered secondary diamine may be suitablefor use in the prepolymer. Without being bound to any particular theory,it is believed that an amine with a high level of stearic hindrance,e.g., a tertiary butyl group on the nitrogen atom, has a slower reactionrate than an amine with no hindrance or a low level of hindrance. Forexample, 4,4′-bis-(sec-butylamino)-dicyclohexylmethane (CLEARLINK® 1000)may be suitable for use in combination with an isocyanate to form thepolyurea prepolymer.

Any isocyanate available to one of ordinary skill in the art is suitablefor use in the polyurea prepolymer. Isocyanates for use with the presentinvention include aliphatic, cycloaliphatic, araliphatic, aromatic, anyderivatives thereof, and combinations of these compounds having two ormore isocyanate (NCO) groups per molecule. The isocyanates may beorganic polyisocyanate-terminated prepolymers. The isocyanate-containingreactable component may also include any isocyanate-functional monomer,dimer, trimer, or multimeric adduct thereof, prepolymer,quasi-prepolymer, or mixtures thereof. Isocyanate-functional compoundsmay include monoisocyanates or polyisocyanates that include anyisocyanate functionality of two or more.

Suitable isocyanate-containing components include diisocyanates havingthe generic structure: O═C═N—R—N═C═O, where R is preferably a cyclic,aromatic, or linear or branched hydrocarbon moiety containing from about1 to about 20 carbon atoms. The diisocyanate may also contain one ormore cyclic groups or one or more phenyl groups. When multiple cyclic oraromatic groups are present, linear and/or branched hydrocarbonscontaining from about 1 to about 10 carbon atoms can be present asspacers between the cyclic or aromatic groups. In some cases, the cyclicor aromatic group(s) may be substituted at the 2-, 3-, and/or4-positions, or at the ortho-, meta-, and/or para-positions,respectively. Substituted groups may include, but are not limited to,halogens, primary, secondary, or tertiary hydrocarbon groups, or amixture thereof.

Examples of diisocyanates that can be used with the present inventioninclude, but are not limited to, substituted and isomeric mixturesincluding 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate (MDI);3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI); toluene diisocyanate(TDI); polymeric MDI; carbodiimide-modified liquid 4,4′-diphenylmethanediisocyanate; para-phenylene diisocyanate (PPDI); meta-phenylenediisocyanate (MPDI); triphenyl methane-4,4′- and triphenylmethane-4,4′-triisocyanate; naphthylene-1,5-diisocyanate; 2,4′-, 4,4′-,and 2,2-biphenyl diisocyanate; polyphenyl polymethylene polyisocyanate(PMDI); mixtures of MDI and PMDI; mixtures of PMDI and TDI; ethylenediisocyanate; propylene-1,2-diisocyanate;tetramethylene-1,2-diisocyanate; tetramethylene-1,3-diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (HDI);octamethylene diisocyanate; decamethylene diisocyanate;2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethanediisocyanate (H₁₂MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; 1,2-, 1,3-, and 1,4-phenylenediisocyanate; aromatic aliphatic isocyanate, such as 1,2-, 1,3-, and1,4-xylene diisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, isocyanurateof isophorone diisocyanate, and mixtures thereof; dimerized uredione ofany polyisocyanate, such as uretdione of toluene diisocyanate, uretdioneof hexamethylene diisocyanate, and mixtures thereof; modifiedpolyisocyanate derived from the above isocyanates and polyisocyanates;and mixtures thereof.

Examples of saturated diisocyanates that can be used with the presentinvention include, but are not limited to, ethylene diisocyanate;propylene-1,2-diisocyanate; tetramethylene diisocyanate;tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (HDI);octamethylene diisocyanate; decamethylene diisocyanate;2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylenediisocyanate; dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate (HTDI);2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate;4,4′-dicyclohexyl diisocyanate; 2,4′-dicyclohexyl diisocyanate;1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate;1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexanediisocyanate; 4,4′-bis(isocyanatomethyl) dicyclohexane;2,4′-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate(IPDI); triisocyanate of HDI; triisocyanate of2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI); 4,4′-dicyclohexylmethanediisocyanate (H₁₂MDI); 2,4-hexahydrotoluene diisocyanate;2,6-hexahydrotoluene diisocyanate; and mixtures thereof. Aromaticaliphatic isocyanates may also be used to form light stable materials.Examples of such isocyanates include 1,2-, 1,3-, and 1,4-xylenediisocyanate; meta-tetramethylxylene diisocyanate (m-TMXDI);para-tetramethylxylene diisocyanate (p-TMXDI); trimerized isocyanurateof any polyisocyanate, such as isocyanurate of toluene diisocyanate,trimer of diphenylmethane diisocyanate, trimer of tetramethylxylenediisocyanate, isocyanurate of hexamethylene diisocyanate, isocyanurateof isophorone diisocyanate, and mixtures thereof; dimerized uredione ofany polyisocyanate, such as uretdione of toluene diisocyanate, uretdioneof hexamethylene diisocyanate, and mixtures thereof; modifiedpolyisocyanate derived from the above isocyanates and polyisocyanates;and mixtures thereof. In addition, the aromatic aliphatic isocyanatesmay be mixed with any of the saturated isocyanates listed above for thepurposes of this invention.

The number of unreacted NCO groups in the polyurea prepolymer ofisocyanate and polyether amine may be varied to control such factors asthe speed of the reaction, the resultant hardness of the composition,and the like. For instance, the number of unreacted NCO groups in thepolyurea prepolymer of isocyanate and polyether amine may be less thanabout 14 percent. In one embodiment, the polyurea prepolymer has fromabout 5 percent to about 11 percent unreacted NCO groups, and even morepreferably has from about 6 to about 9.5 percent unreacted NCO groups.In one embodiment, the percentage of unreacted NCO groups is about 3percent to about 9 percent. Alternatively, the percentage of unreactedNCO groups in the polyurea prepolymer may be about 7.5 percent or less,and more preferably, about 7 percent or less. In another embodiment, theunreacted NCO content is from about 2.5 percent to about 7.5 percent,and more preferably from about 4 percent to about 6.5 percent.

When formed, polyurea prepolymers may contain about 10 percent to about20 percent by weight of the prepolymer of free isocyanate monomer. Thus,in one embodiment, the polyurea prepolymer may be stripped of the freeisocyanate monomer. For example, after stripping, the prepolymer maycontain about 1 percent or less free isocyanate monomer. In anotherembodiment, the prepolymer contains about 0.5 percent by weight or lessof free isocyanate monomer.

The polyether amine may be blended with additional polyols to formulatecopolymers that are reacted with excess isocyanate to form the polyureaprepolymer. In one embodiment, less than about 30 percent polyol byweight of the copolymer is blended with the saturated polyether amine.In another embodiment, less than about 20 percent polyol by weight ofthe copolymer, preferably less than about 15 percent by weight of thecopolymer, is blended with the polyether amine. The polyols listed abovewith respect to the polyurethane prepolymer, e.g., polyether polyols,polycaprolactone polyols, polyester polyols, polycarbonate polyols,hydrocarbon polyols, other polyols, and mixtures thereof, are alsosuitable for blending with the polyether amine. The molecular weight ofthese polymers may be from about 200 to about 4000, but also may be fromabout 1000 to about 3000, and more preferably are from about 1500 toabout 2500.

The polyurea composition can be formed by crosslinking the polyureaprepolymer with a single curing agent or a blend of curing agents. Thecuring agent of the invention is preferably an amine-terminated curingagent, more preferably a secondary diamine curing agent so that thecomposition contains only urea linkages. In one embodiment, theamine-terminated curing agent may have a molecular weight of about 64 orgreater. In another embodiment, the molecular weight of the amine-curingagent is about 2000 or less. As discussed above, certainamine-terminated curing agents may be modified with a compatibleamine-terminated freezing point depressing agent or mixture ofcompatible freezing point depressing agents.

Suitable amine-terminated curing agents include, but are not limited to,ethylene diamine; hexamethylene diamine; 1-methyl-2,6-cyclohexyldiamine; tetrahydroxypropylene ethylene diamine; 2,2,4- and2,4,4-trimethyl-1,6-hexanediamine;4,4′-bis-(sec-butylamino)-dicyclohexylmethane;1,4-bis-(sec-butylamino)-cyclohexane;1,2-bis-(sec-butylamino)-cyclohexane; derivatives of4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 4,4′-dicyclohexylmethanediamine; 1,4-cyclohexane-bis-(methylamine);1,3-cyclohexane-bis-(methylamine); diethylene glycoldi-(aminopropyl)ether; 2-methylpentamethylene-diamine;diaminocyclohexane; diethylene triamine; triethylene tetramine;tetraethylene pentamine; propylene diamine; 1,3-diaminopropane;dimethylamino propylamine; diethylamino propylamine; dipropylenetriamine; imido-bis-propylamine; monoethanolamine, diethanolamine;triethanolamine; monoisopropanolamine, diisopropanolamine;isophoronediamine; 4,4′-methylenebis-(2-chloroaniline);3,5;dimethylthio-2,4-toluenediamine;3,5-dimethylthio-2,6-toluenediamine; 3,5-diethylthio-2,4-toluenediamine;3,5;diethylthio-2,6-toluenediamine;4,4′-bis-(sec-butylamino)-diphenylmethane and derivatives thereof;1,4-bis-(sec-butylamino)-benzene; 1,2-bis-(sec-butylamino)-benzene;N,N′-dialkylamino-diphenylmethane;N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylene diamine;trimethyleneglycol-di-p-aminobenzoate;polytetramethyleneoxide-di-p-aminobenzoate;4,4′-methylenebis-(3-chloro-2,6-diethyleneaniline);4,4′-methylenebis-(2,6-diethylaniline); meta-phenylenediamine;paraphenylenediamine; and mixtures thereof. In one embodiment, theamine-terminated curing agent is4,4′-bis-(sec-butylamino)-dicyclohexylmethane.

Suitable saturated amine-terminated curing agents include, but are notlimited to, ethylene diamine; hexamethylene diamine;1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene diamine;2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine;4,4′-bis-(sec-butylamino)-dicyclohexylmethane;1,4-bis-(sec-butylamino)-cyclohexane;1,2-bis-(sec-butylamino)-cyclohexane; derivatives of4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 4,4′-dicyclohexylmethanediamine; 4,4′-methylenebis-(2,6-diethylaminocyclohexane;1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine);diethylene glycol di-(aminopropyl)ether; 2-methylpentamethylene-diamine;diaminocyclohexane; diethylene triamine; triethylene tetramine;tetraethylene pentamine; propylene diamine; 1,3-diaminopropane;dimethylamino propylamine; diethylamino propylamine;imido-bis-propylamine; monoethanolamine, diethanolamine;triethanolamine; monoisopropanolamine, diisopropanolamine;isophoronediamine; triisopropanolamine; and mixtures thereof. Inaddition, any of the polyether amines listed above may be used as curingagents to react with the polyurea prepolymers.

Suitable catalysts include, but are not limited to bismuth catalyst,oleic acid, triethylenediamine (DABCO®-33LV), di-butyltin dilaurate(DABCO®-T12) and acetic acid. The most preferred catalyst is di-butyltindilaurate (DABCO®-T12). DABCO® materials are manufactured by AirProducts and Chemicals, Inc.

Thermoplastic materials may be blended with other thermoplasticmaterials, but thermosetting materials are difficult if not impossibleto blend homogeneously after the thermosetting materials are formed.Preferably, the saturated polyurethane comprises from about 1% to about100%, more preferably from about 10% to about 75% of the covercomposition and/or the intermediate layer composition. About 90% toabout 10%, more preferably from about 90% to about 25% of the coverand/or the intermediate layer composition is comprised of one or moreother polymers and/or other materials as described below. Such polymersinclude, but are not limited to polyurethane/polyurea ionomers,polyurethanes or polyureas, epoxy resins, polyethylenes, polyamides andpolyesters, polycarbonates and polyacrylin. Unless otherwise statedherein, all percentages are given in percent by weight of the totalcomposition of the golf ball layer in question.

Polyurethane prepolymers are produced by combining at least one polyol,such as a polyether, polycaprolactone, polycarbonate, or polyester, andat least one isocyanate. Thermosetting polyurethanes are obtained bycuring at least one polyurethane prepolymer with a curing agent selectedfrom a polyamine, triol or tetraol. Thermoplastic polyurethanes areobtained by curing at least one polyurethane prepolymer with a diolcuring agent. The choice of the curatives is critical because someurethane elastomers that are cured with a diol and/or blends of diols donot produce urethane elastomers with the impact resistance required in agolf ball cover. Blending the polyamine curatives with diol curedurethane elastomeric formulations leads to the production of thermoseturethanes with improved impact and cut resistance.

Thermoplastic polyurethanes may be blended with suitable materials toproduce a thermoplastic end product. Examples of such additionalmaterials may include ionomers such as the SURLYN®, ESCOR® and IOTEK®copolymers described above.

Other suitable materials which may be combined with the saturatedpolyurethanes in forming the cover and/or intermediate layer(s) of thegolf balls of the invention include ionic or non-ionic polyurethanes andpolyureas, epoxy resins, polyethylenes, polyamides and polyesters. Forexample, the cover and/or intermediate layer may be formed from a blendof at least one saturated polyurethane and thermoplastic or thermosetionic and non-ionic urethanes and polyurethanes, cationic urethaneionomers and urethane epoxies, ionic and non-ionic polyureas, and blendsthereof. Examples of suitable urethane ionomers are disclosed in U.S.Pat. No. 5,692,974, the disclosure of which is hereby incorporated byreference in its entirety. Other examples of suitable polyurethanes aredescribed in U.S. Pat. No. 5,334,673. Examples of appropriate polyureasare discussed in U.S. Pat. No. 5,484,870 and examples of suitablepolyurethanes cured with epoxy group containing curing agents aredisclosed in U.S. Pat. No. 5,908,358, the disclosures of which arehereby incorporated herein by reference in their entirety.

A variety of conventional components can be added to the covercompositions of the present invention. These include, but are notlimited to, white pigment such as TiO₂, ZnO, optical brighteners,surfactants, processing aids, foaming agents, density-controllingfillers, UV stabilizers and light stabilizers. Saturated polyurethanesare resistant to discoloration. However, they are not immune todeterioration in their mechanical properties upon weathering. Additionof UV absorbers and light stabilizers therefore helps to maintain thetensile strength and elongation of the saturated polyurethaneelastomers. Suitable UV absorbers and light stabilizers include TINUVIN®328, TINUVIN® 213, TINUVIN® 765, TINUVIN® 770 and TINUVIN® 622. Thepreferred UV absorber is TINUVIN® 328, and the preferred lightstabilizer is TINUVIN® 765. TINUVIN® products are available fromCiba-Geigy. Dyes, as well as optical brighteners and fluorescentpigments may also be included in the golf ball covers produced withpolymers formed according to the present invention. Such additionalingredients may be added in any amounts that will achieve their desiredpurpose.

Any method known to one of ordinary skill in the art may be used topolyurethanes of the present invention. One commonly employed method,known in the art as a one-shot method, involves concurrent mixing of thepolyisocyanate, polyol, and curing agent. This method results in amixture that is inhomogeneous (more random) and affords the manufacturerless control over the molecular structure of the resultant composition.A preferred method of mixing is known as a prepolymer method. In thismethod, the polyisocyanate and the polyol are mixed separately prior toaddition of the curing agent. This method produces a more homogeneousmixture, resulting in a more consistent polymer composition. Othermethods suitable for forming the layers of the present invention includereaction injection molding (“RIM”), liquid injection molding (“LIM”),and pre-reacting the components to form an injection moldablethermoplastic polyurethane and then injection molding, all of which areknown to one of ordinary skill in the art.

Additional components which can be added to the polyurethane compositioninclude UV stabilizers and other dyes, as well as optical brightenersand fluorescent pigments and dyes. Such additional ingredients may beadded in any amounts that will achieve their desired purpose.

The cover can also be made from ionomeric polymers or blends thereof, asdescribed above.

It has been found by the present invention that the use of a castable,reactive material, which is applied in a fluid form, makes it possibleto obtain very thin outer cover layers on golf balls. Specifically, ithas been found that castable, reactive liquids, which react to form aurethane elastomer material, provide desirable thin outer cover layers.

The castable, reactive liquid employed to form the urethane elastomermaterial can be applied over the core using a variety of applicationtechniques such as spraying, dipping, spin coating, or flow coatingmethods which are well known in the art. An example of a suitablecoating technique is that which is disclosed in U.S. Pat. No. 5,733,428,the disclosure of which is hereby incorporated by reference in itsentirety.

The cover is preferably formed around the core by mixing and introducingthe material in the mold halves. It is important that the viscosity bemeasured over time, so that the subsequent steps of filling each moldhalf, introducing the core into one half and closing the mold can beproperly timed for accomplishing centering of the core cover halvesfusion and achieving overall uniformity. Suitable viscosity range of thecuring urethane mix for introducing cores into the mold halves isdetermined to be approximately between about 2,000 cP and about 30,000cP, with the preferred range of about 8,000 cP to about 15,000 cP.

To start the cover formation, mixing of the prepolymer and curative isaccomplished in motorized mixer including mixing head by feeding throughlines metered amounts of curative and prepolymer. Top preheated moldhalves are filled and placed in fixture units using centering pinsmoving into holes in each mold. At a later time, a bottom mold half or aseries of bottom mold halves have similar mixture amounts introducedinto the cavity. After the reacting materials have resided in top moldhalves for about 40 to about 80 seconds, a core is lowered at acontrolled speed into the gelling reacting mixture.

A ball cup holds the ball core through reduced pressure (or partialvacuum). Upon location of the coated core in the halves of the moldafter gelling for about 40 to about 80 seconds, the vacuum is releasedallowing core to be released. The mold halves, with core and solidifiedcover half thereon, are removed from the centering fixture unit,inverted and mated with other mold halves which, at an appropriate timeearlier, have had a selected quantity of reacting polyurethaneprepolymer and curing agent introduced therein to commence gelling.Similarly, U.S. Pat. No. 5,006,297 to Brown et al. and U.S. Pat. No.5,334,673 to Wu both also disclose suitable molding techniques which maybe utilized to apply the castable reactive liquids employed in thepresent invention. Further, U.S. Pat. Nos. 6,180,040 and 6,180,722disclose methods of preparing dual core golf balls. The disclosures ofthese patents are hereby incorporated by reference in their entirety.However, the method of the invention is not limited to the use of thesetechniques.

Additionally, other suitable core and cover materials are disclosed inU.S. Pat. No. 5,919,100 and International Publication Nos. WO 00/23519and WO 01/29129. These disclosures are incorporated by reference intheir entireties. Preferably, inner core 12 is made from a polybutadienerubber material, and cover layer 16 is made from a compositioncomprising a thermoset or thermoplastic urethane or a compositioncomprising an ionomer resin.

Referring back to FIG. 2, in one embodiment a multi-layer golf ball 20comprises at least 3 pieces: an inner core 22, an outer core layer 24,and a cover 26. Inner core 22 has a diameter of about 1.40 inches, anAtti compression of less than 60, preferably less than 45, and mostpreferably less than 40. The compression preferably a number in therange from about 5 to about 60, more preferably from about 10 to about50, and most preferably from about 15 to about 40. Inner core 22 alsohas a specific gravity of less than the outer core layer, preferablyless than 1.15, and most preferably less than 1.10.

Accordingly, outer core layer 24 has a specific gravity greater thaninner core 22, preferably greater than 1.15, more preferably greaterthan 1.20, and most preferably greater than 1.25. The Shore D hardnessof outer core layer 24 is at least 55, with the flex modulus of outercore layer 24 preferably greater than the flex modulus of inner core 22.Outer core layer 24 also has a thickness of about 0.10 inches.

Cover layer 26 is at least about 0.04 inches thick and comprises a stiffionomer blend, with a Shore D hardness of at least 60 and preferably atleast 65. The flexural modulus of cover 26 is preferably at least 60ksi. A preferred relationship between the Shore D hardness and theflexural modulus of cover layer 26, when the flexural modulus ismeasured in ksi and is at least 58 ksi, is as follows:

Preferably: 1.0>(Shore D_(cover))/(Flex Modulus_(cover))

More preferably: 0.9>(Shore D_(cover))/(Flex Modulus_(cover))

Most preferably: 0.8>(Shore D_(cover))/(Flex Modulus_(cover))

These relationships provide for a golf ball with lower spin off thetees, yet increased spin on approach shots to the green. Less advancedgolfers benefit from added driving distances, while more skilled playersreceive more control of the ball around the greens.

In a preferred embodiment, cover layer 26 comprises an acrylic acidionomer (Dow or Schulman type) having an acid content of between about13% and 16%, although as will be recognized by those skilled in the artand discussed above, the type of ionomer and acid content range mayvary. The ionomer is preferably neutralized with a cation of sodium(Na), lithium (Li), zinc (Zn), magnesium (Mg), or calcium (Ca), e.g., asdiscussed above, but again, as will be recognized by those skilled inthe art, the cation used may vary.

In another embodiment, inner core 22, outer core layer 24, and cover 26are all substantially similar to the preceding embodiments, but thematerials, properties, and dimensions are selected as to result in a CORgradient of slow to fast. For example, inner core 22 has a lower CORthan the subassembly comprising the inner core 22 and the outer corelayer 24, which in turn has a lower COR than the entire golf ball 20comprising the inner core 22, outer core 24, and cover 26. This slow tofast COR gradient provides for the ball to have a greater initialvelocity and less spin when being hit off of the tees, yet still havehigher spin rates when being hit on approach shots into the greens. Thisresults in more forgiving drives that will travel longer distances forless skilled players with slower swing speeds, but more control andprecision for advanced players with faster swing speeds.

Another embodiment of the inventive golf ball is substantially similarto the aforementioned embodiments, except that a core layer, eitherinner core 22 or outer core layer 24, comprises an HNP. In thisembodiment, it is preferred that inner core 22 comprises an unfilled HNPwherein the specific gravity of the inner core is less than 1.0, mostpreferably about 0.95. This low specific gravity with an unfilled HNP atthe center of the ball increases the moment of inertia of the ball,reducing its spin rate at the moment of striking and allowing it totravel longer distances off the tee.

Referring back to FIG. 1, in another embodiment the multi-layer golfball 10 has at least 4 pieces, as it comprises an inner core 12, atleast one intermediate core layer 14, an outer core layer 16, and acover layer 18. In this embodiment the core subassembly includes 3pieces that make up two separate subassemblies. One is an innersubassembly made up of inner core 12 plus at least one intermediate corelayer 14, while the other comprises inner core 12 plus intermediate corelayer 14 plus outer core layer 16. Additional embodiments may havemultiple intermediate core layers 14 such that multiple subassembliesencompassing each successive intermediate core layer may be present. Inthe 3 piece core embodiment, the specific gravity of the inner core 12is less than the specific gravity of the intermediate core layer 14,which in turn is less than the outer core layer 16. Cover layer 18 alsohas a specific gravity that is less than outer core layer 16. The volumeof inner core 12 in the embodiment shown in FIG. 1 is larger than thevolume of outer core layer 16, and both are larger than the volume ofcover layer 18. The volume of the layers and the hardness of the layershave an inverse relationship, however. Cover layer 18 has a Shore Dhardness larger than outer core layer 16, which in turn has a largerShore D hardness than inner core 12. If multiple intermediate corelayers are added, it is preferred that each successive intermediate corelayer have a larger specific gravity, larger Shore D hardness, andsmaller volume than the preceding intermediate core layer closer toinner core 12. The hardness of the outer portions of golf ball 10, suchas outer core layer 16 and cover layer 18, is advantageous tolesser-skilled players due to its comforting sound and added distancethat results when striking the ball, but the decreased hardness insidethe ball is important to augment feel and control, similar totraditional wound balls, for advanced players.

Intermediate layer 14 may comprise materials such as thermosettingpolybutadiene or other diene rubber based formulations, thermoplastic orthermosetting polyurethanes, polyureas, partially or fully neutralizedHNP'S, polyolefins including metallocene or other single site catalyzedpolymers, polymers comprising silicone, polyamides, polyesters,polyether amides, polyester amides, and other materials known in theart. Intermediate layer 14 can be any layer between the innermost coreand the outermost layer, and there can be a plurality of intermediatelayers 14.

As used herein, the following terms are defined as:

Coefficient of Restitution (COR)—The ratio of the relative velocitybetween two objects after direct impact to the relative velocity beforeimpact. As a result, the CoR can vary from 0 to 1, with 1 beingequivalent to a perfectly or completely elastic collision and 0 beingequivalent to a perfectly plastic or completely inelastic collision.Since a ball's CoR directly influences the ball's initial velocity afterclub collision and travel distance, golf ball manufacturers areinterested in this characteristic for designing and testing golf balls.

One conventional technique for measuring COR uses a golf ball or golfball subassembly, an air cannon, and a stationary vertical steel plate.The steel plate provides an impact surface weighing about 100 pounds orabout 45 kilograms. A pair of ballistic light screens are spaced apartand located between the air cannon and the steel plate. The ball isfired from the air cannon toward the steel plate over a range of testvelocities from 50 ft/sec to 180 ft/sec. All COR data presented in thisapplication is measured using a speed of 125 ft/sec. As the ball travelstoward the steel plate, it activates each light screen so that the timeat each light screen is recorded. This provides an incoming time periodproportional to the ball's incoming velocity. The ball impacts the steelplate and rebounds though the light screens, which again measures thetime period required to transit between the light screens. This providesan outgoing transit time period proportional to the ball's outgoingvelocity. The COR can be calculated by the ratio of the outgoing transittime period to the incoming transit time period.

Compression—At one time compression was used to describe the quality ofa golf ball according to the tightness of the windings around a threepiece ball core. In solid-core golf balls, compression now onlyindicates how much a ball will “deform” under a compressive force. It ismeasured by applying a spring-loaded force to the golf ball center, golfball core or the golf ball to be examined, with a manual instrument (an“Atti gauge”) manufactured by the Atti Engineering Company of UnionCity, N.J. This machine, equipped with a Federal Dial Gauge, ModelD81-C, employs a calibrated spring under a known load. The sphere to betested is forced a distance of 0.2 inch (5 mm) against this spring. Ifthe spring, in turn, compresses 0.2 inch, the compression is rated at100; if the spring compresses 0.1 inch, the compression value is ratedas 0. Thus more compressible, softer materials will have lower Atticompression values than harder, less compressible materials.

Flexural Modulus—The ratio of flexural stress to flexural strain withinthe elastic limit (when measured in the flexural mode) and is similar tothe tensile modulus. This property is used to indicate the bendingstiffness of a material and is measured according to ASTM Test MethodD790.

Hardness—the characteristic of a solid material expressing itsresistance to permanent deformation. It can be measured on numerousscales, but all hardness data in this application is measured using aShore D Durometer. Testing is done according to ASTM Test Method D2240.The results obtained from this test are a useful measure of relativeresistance to indentation of various grades of polymers.

Ionomer—a polymer, specifically a polyelectrolyte, that comprisescopolymers containing both electrically neutral repeating units and afraction of ionic units (usually no more than 15%). Due to ionicinteractions in discrete regions of the material, ionomers typicallyhave unique physical properties.

Specific Gravity—a ratio of the density of a substance relative to thedensity of another substance, most typically water. Because water has adensity of 1 g/cc, the specific gravity of a material will usually beequal to the density, but dimensionless because the units cancel.Specific gravity is measured according to ASTM Test Method D792.

Unless otherwise expressly specified, all of the numerical ranges,amounts, values and percentages such as those for amounts of materials,and others in the specification may be read as if prefaced by the word“about” even though the term “about” may not expressly appear with thevalue, amount, or range. Accordingly, unless indicated to the contrary,the numerical parameters set forth in the specification and attachedclaims are approximations that may vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, may inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.While it is apparent that the illustrative embodiments of the inventiondisclosed herein fulfill the objectives stated above, it is appreciatedthat numerous modifications and other embodiments may be devised bythose skilled in the art. Therefore, it will be understood that theappended claims are intended to cover all such modifications andembodiments which would come within the spirit and scope of the presentinvention.

1. A golf ball comprising: an inner core having a compression of lessthan about 40; at least one intermediate layer surrounding the innercore, having a hardness of at least about 55 Shore D, and a specificgravity greater than a specific gravity of the inner core; and a coversurrounding the intermediate layer comprised of an acrylic acid ionomerhaving an acid content of between 13% and 16%; wherein the inner corehas a hardness less than a hardness of the intermediate layer andwherein a ratio of flexural modulus (ksi) to Shore D hardness for thecover is less than about 1.0 and a first COR of the inner core and theintermediate layer is less than a second COR of the entire ball.
 2. Thegolf ball of claim 1, wherein the intermediate layer has a higherflexural modulus than a flexural modulus of the inner core.
 3. The golfball of claim 1, wherein the inner core has a diameter of about 1.4inches or less and the intermediate layer has a thickness of about 0.1inches or less.
 4. The golf ball of claim 1, wherein the specificgravity of the inner core is less than about 1.15.
 5. The golf ball ofclaim 4, wherein the specific gravity of the inner core is less thanabout 1.05.
 6. The golf ball of claim 1, wherein the specific gravity ofthe intermediate layer is greater than about 1.15.
 7. The golf ball ofclaim 6, wherein the specific gravity of the intermediate layer isgreater than about 1.20.
 8. The golf ball of claim 7, wherein thespecific gravity of the intermediate layer is greater than about 1.25.9. The golf ball of claim 1, wherein the cover has a hardness of atleast about 60 Shore D, a modulus of least about 60 ksi, and a thicknessof about 0.03 to about 0.5 inches.
 10. The golf ball of claim 9, whereinthe hardness of the cover is at least about 65 Shore D.
 11. A golf ballcomprising: an inner core; at least one intermediate core layersurrounding the inner core having a specific gravity larger than aspecific gravity of the inner core; at least one outer core layersurrounding the intermediate core layer having a specific gravity largerthan the specific gravity of the intermediate core layer; and a coversurrounding the outer core layer having a specific gravity smaller thanthe specific gravity of the outer core layer, wherein a ratio offlexural modulus (ksi) to Shore D hardness for the cover is less thanabout 1.0.
 12. The golf ball of claim 11, wherein a volume of the innercore layer is greater than a volume of the outer core layer, and whereina volume of the cover layer is less than the volume of the outer corelayer.
 13. The golf ball of claim 11, wherein a hardness of the innercore is less than a hardness of the outer core, and wherein a hardnessof the cover is greater than the hardness of the outer core.
 14. A golfball comprising: an inner core having a compression of less than about60; at least one outer core layer surrounding the inner core, having ahardness of at least about 55 Shore D, and a specific gravity greaterthan a specific gravity of the inner core; and a cover surrounding theouter core layer; wherein the inner core has a hardness less than ahardness of the outer core, and wherein the inner core layer comprises aunfilled highly neutralized thermoplastic ionomer (HNP) having aspecific gravity of less than 0.95.
 15. The golf ball of claim 14,wherein a ratio of the Shore D hardness to the flexural modulus of thecover layer is less than about 1.0.
 16. The golf ball of claim 15,wherein said ratio is less than about 0.95.
 17. The golf ball of claim15, wherein said ratio is less than about 0.90.
 18. The golf ball ofclaim 14, wherein the compression of the inner core is less than about40.
 19. The golf ball of claim 18, wherein the compression of the innercore is less than about 30.